Description of problem:

Attempting to include both headers with the same ifdef ("IB_USER_IOCTL_VERBS_H") wrapper can produce a failure depending on order of include, as the files are not identical.

Problem headers:
  /usr/include/rdma/ib_user_ioctl_verbs.h 
  /usr/include/infiniband/ib_user_ioctl_verbs.h


Version-Release number of selected component (if applicable):
  /usr/include/infiniband/ib_user_ioctl_verbs.h rdma-core-devel-32.0-4.el8.x86_64
  /usr/include/rdma/ib_user_ioctl_verbs.h       kernel-headers-4.18.0-305.el8.x86_64

There appear to be differences in other RHEL versions, though not the same fields.

How reproducible:

Compile simple c file with different defines.

Simple c file:
====
#ifdef BAD_ORDER
# include <rdma/ib_user_ioctl_verbs.h>
# include <infiniband/ib_user_ioctl_verbs.h>
#else
# include <infiniband/ib_user_ioctl_verbs.h>
# include <rdma/ib_user_ioctl_verbs.h>
#endif
int main(int argc, char **argv) {
    enum ib_uverbs_gid_type type = IB_UVERBS_GID_TYPE_IB;
    (void)type;
    return 0;
}
====
Steps to Reproduce:
1. gcc -DBAD_ORDER rdma.c


Actual results:
Compile this with "-DBAD_ORDER":

rdma.c: In function 'main':
rdma.c:11:7: error: variable 'type' has initializer but incomplete type
  enum ib_uverbs_gid_type type = IB_UVERBS_GID_TYPE_IB;
       ^~~~~~~~~~~~~~~~~~
rdma.c:11:33: error: 'IB_UVERBS_GID_TYPE_IB' undeclared (first use in this function); did you mean 'IB_UVERBS_PCF_TRAP_SUP'?
  enum ib_uverbs_gid_type type = IB_UVERBS_GID_TYPE_IB;
                                 ^~~~~~~~~~~~~~~~~~~~~
                                 IB_UVERBS_PCF_TRAP_SUP
rdma.c:11:33: note: each undeclared identifier is reported only once for each function it appears in
rdma.c:11:26: error: storage size of 'type' isn't known
  enum ib_uverbs_gid_type type = IB_UVERBS_GID_TYPE_IB;
                          ^~~~

Expected results:
No error

Additional info:
These files can de indirectly included from higher-level includes like verbs.h, etc.