hw/rdma: Fix 32-bit compilation

Use the correct printf formats, so that a 32-bit compile doesn't spit
out lots of warnings about %lx being incompatible with uint64_t.

Suggested-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180322095220.9976-4-yuval.shaia@oracle.com>
Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>