Verified the bug with qemu-kvm-6.0.0-17.module+el8.5.0+11173+c9fce0bb.ppc64le, the RHEL-AV 8.5 new machine type is added successfully.

[root@ibm-p8-garrison-03 ~]# /usr/libexec/qemu-kvm  -machine ? 
Supported machines are:
none                 empty machine
pseries-rhel7.2.0    pSeries Logical Partition (PAPR compliant)
pseries-rhel7.3.0    pSeries Logical Partition (PAPR compliant)
pseries-rhel7.3.0-sxxm pSeries Logical Partition (PAPR compliant)
pseries-rhel7.4.0    pSeries Logical Partition (PAPR compliant)
pseries-rhel7.4.0-sxxm pSeries Logical Partition (PAPR compliant)
pseries-rhel7.5.0    pSeries Logical Partition (PAPR compliant)
pseries-rhel7.5.0-sxxm pSeries Logical Partition (PAPR compliant)
pseries-rhel7.6.0    pSeries Logical Partition (PAPR compliant)
pseries-rhel7.6.0-sxxm pSeries Logical Partition (PAPR compliant)
pseries-rhel8.0.0    pSeries Logical Partition (PAPR compliant)
pseries-rhel8.1.0    pSeries Logical Partition (PAPR compliant)
pseries-rhel8.2.0    pSeries Logical Partition (PAPR compliant)
pseries-rhel8.3.0    pSeries Logical Partition (PAPR compliant)
pseries-rhel8.4.0    pSeries Logical Partition (PAPR compliant)
pseries              pSeries Logical Partition (PAPR compliant) (alias of pseries-rhel8.5.0)
pseries-rhel8.5.0    pSeries Logical Partition (PAPR compliant) (default)

# /usr/libexec/qemu-kvm  -machine pseries-rhel8.5.0
VNC server running on ::1:5900

#/usr/libexec/qemu-kvm -S -name avocado-vt-vm1 -sandbox on -machine pseries -nodefaults -device VGA,bus=pci.0,addr=0x2 -device i6300esb,bus=pci.0,addr=0x3 -watchdog-action reset -device pci-bridge,id=pci_bridge,bus=pci.0,addr=0x4,chassis_nr=1 -m 8192 -smp 4,maxcpus=4,cores=2,threads=1,sockets=2 -cpu host -chardev socket,id=qmp_id_qmpmonitor1,wait=off,server=on,path=/tmp/avocado_1erxyw3a/monitor-qmpmonitor1-20210530-212633-ZaXbCJz1 -mon chardev=qmp_id_qmpmonitor1,mode=control -chardev socket,id=qmp_id_catch_monitor,wait=off,server=on,path=/tmp/avocado_1erxyw3a/monitor-catch_monitor-20210530-212633-ZaXbCJz1 -mon chardev=qmp_id_catch_monitor,mode=control -chardev socket,id=chardev_serial0,wait=off,server=on,path=/tmp/avocado_1erxyw3a/serial-serial0-20210530-212633-ZaXbCJz1 -device spapr-vty,id=serial0,reg=0x30000000,chardev=chardev_serial0 -object rng-random,filename=/dev/urandom,id=passthrough-cHaXBjJp -device virtio-rng-pci,id=virtio-rng-pci-VavrZxlB,rng=passthrough-cHaXBjJp,bus=pci.0,addr=0x5 -device qemu-xhci,id=usb1,bus=pci.0,addr=0x6 -device usb-tablet,id=usb-tablet1,bus=usb1.0,port=1 -blockdev node-name=file_image1,driver=file,auto-read-only=on,discard=unmap,aio=threads,filename=/home/kar/vt_test_images/rhel850-ppc64le-virtio.qcow2,cache.direct=off,cache.no-flush=on -blockdev node-name=drive_image1,driver=qcow2,read-only=off,cache.direct=off,cache.no-flush=on,file=file_image1 -device virtio-blk-pci,id=image1,drive=drive_image1,bootindex=1,write-cache=on,bus=pci.0,addr=0x7 -device virtio-net-pci,mac=9a:0f:02:cf:9f:db,id=idUhfKXC,netdev=idMK6Or2,bus=pci.0,addr=0x8 -netdev tap,id=idMK6Or2,vhost=on,vhostfd=20,fd=14 -device virtio-scsi-pci,id=virtio_scsi_pci0,bus=pci.0,addr=0x9 -blockdev node-name=file_cd1,driver=file,auto-read-only=on,discard=unmap,aio=threads,filename=/var/lib/avocado/data/avocado-vt/isos/linux/RHEL-8.5.0-20210527.n.0-ppc64le-dvd1.iso,cache.direct=off,cache.no-flush=on -blockdev node-name=drive_cd1,driver=raw,read-only=on,cache.direct=off,cache.no-flush=on,file=file_cd1 -device scsi-cd,id=cd1,drive=drive_cd1,bootindex=2,write-cache=on -blockdev node-name=file_unattended,driver=file,auto-read-only=on,discard=unmap,aio=threads,filename=/home/kar/vt_test_images/rhel850-ppc64le/ks.iso,cache.direct=off,cache.no-flush=on -blockdev node-name=drive_unattended,driver=raw,read-only=on,cache.direct=off,cache.no-flush=on,file=file_unattended -device scsi-cd,id=unattended,drive=drive_unattended,bootindex=3,write-cache=on -kernel /home/kar/vt_test_images/rhel850-ppc64le/vmlinuz -append inst.sshd ksdevice=link inst.repo=cdrom inst.ks=cdrom:/ks.cfg nicdelay=60 biosdevname=0 net.ifnames=0 console=hvc0,38400 console=tty0 -initrd /home/kar/vt_test_images/rhel850-ppc64le/initrd.img -vnc :0 -rtc base=utc,clock=host -boot menu=off,order=cdn,once=d,strict=off -no-shutdown -enable-kvm -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0xa

Setting to verified since the machine type is added.  If there's other issue with this build will file separate bug.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (virt:av bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2021:4684