Description of problem:
/proc/cpuinfo cannot shows correct CPU number after hotplug vCPU by qmp command

Version-Release number of selected component (if applicable):
kernel: 4.18.0-496.el8.s390x
qemu-kvm: qemu-kvm-6.2.0-35.module+el8.9.0+19024+8193e2ac.s390x

How reproducible:
100%

1. boot up guest with
"-smp 5,maxcpus=6,cores=3,threads=1,sockets=2  \"
2. hot-plug 1 vCPU by command in qmp:
"{"execute": "device_add", "arguments": {"id": "vcpu1", "driver": "host-s390x-cpu", "core-id": 5}, "id": "F13T8uRq"}"
3. search the CPU info in /proc/cpuinfo
"grep -c "^processor\b" /proc/cpuinfo"

Actual results:
[root@localhost ~]# grep -c "^processor\b" /proc/cpuinfo
5


Expected results:
[root@localhost ~]# grep -c "^processor\b" /proc/cpuinfo
6

Additional info:
Didn't hit this issue with:

kernel version: 4.18.0-492.el8.s390x
qemu version: qemu-kvm-6.2.0-34.module+el8.9.0+18868+5565e56d.s390x


http://10.0.136.47/7944438/test-results/101-Host_RHEL.m8.u9.v0.product_rhel.nographic.qcow2.virtio_scsi.up.virtio_net.Guest.RHEL.9.3.0.s390x.io-github-autotest-qemu.cpu_device_hotpluggable.hotplug.single_vcpu.with_reboot.shell_reboot.s390-virtio/debug.log