inet_diag.c: Silence gcc warning about different types in conditional expr

In Fedora 23, gcc version 5.3.1 20151207 (Red Hat 5.3.1-2) (GCC):

python-inet_diag/inet_diag.c: In function ‘inet_diag__create’:
python-inet_diag/inet_diag.c:1130:45: warning: pointer type mismatch in conditional expression
         .iov_base = ( req_v2 == 1 ) ? &req2 : &req,

Since we are really dealing with two anonymous struct for different
netlink protocol versions, cast one to (void *) to mean we know what
we're doing.

Cc: James Hulka <james.hulka@gmail.com>
Cc: Jiri Kastner <jkastner@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Jiri Kastner <jkastner@redhat.com>
diff --git a/python-inet_diag/inet_diag.c b/python-inet_diag/inet_diag.c
index dd34b74..a86c294 100644
--- a/python-inet_diag/inet_diag.c
+++ b/python-inet_diag/inet_diag.c
@@ -1127,7 +1127,7 @@
 
     struct iovec iov[3];
     iov[0] = (struct iovec){
-        .iov_base = ( req_v2 == 1 ) ? &req2 : &req,
+        .iov_base = ( req_v2 == 1 ) ? &req2 : (void *)&req,
         .iov_len  = ( req_v2 == 1 ) ? sizeof(req2) : sizeof(req),
     };