net: unix -- Add missing module.h inclusion

Otherwise getting

 | net/unix/diag.c:312:16: error: expected declaration specifiers or ‘...’ before string constant
 | net/unix/diag.c:313:1: error: expected declaration specifiers or ‘...’ before string constant

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/unix/diag.c

@@ -3,6 +3,7 @@
 #include <linux/sock_diag.h>
 #include <linux/unix_diag.h>
 #include <linux/skbuff.h>
+#include <linux/module.h>
 #include <net/netlink.h>
 #include <net/af_unix.h>
 #include <net/tcp_states.h>