hw/rdma: avoid suspicious strncpy() use

hw/rdma: avoid suspicious strncpy() use

gcc (GCC) 9.2.1 20190827 (Red Hat 9.2.1-1) with sanitizers enabled
reports the following error:

  CC      x86_64-softmmu/hw/rdma/vmw/pvrdma_dev_ring.o
In file included from /usr/include/string.h:495,
                 from include/qemu/osdep.h:101,
                 from hw/rdma/vmw/pvrdma_dev_ring.c:16:
In function ‘strncpy’,
    inlined from ‘pvrdma_ring_init’ at hw/rdma/vmw/pvrdma_dev_ring.c:33:5:
/usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ specified bound 32 equals destination size [-Werror=stringop-truncation]
  106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Use pstrcpy() instead of strncpy().  It is guaranteed to NUL-terminate
strings.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Yuval Shaia <yuval.shaia.ml.gmail.com>
Message-Id: <20200316160702.478964-3-stefanha@redhat.com>
Signed-off-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>