[IPV4]: Clean the ip_sockglue.c from some ugly ifdefs

The #idfed CONFIG_IP_MROUTE is sometimes places inside the if-s,
which looks completely bad. Similar ifdefs inside the functions
looks a bit better, but they are also not recommended to be used.

Provide an ifdef-ed ip_mroute_opt() helper to cleanup the code.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/mroute.h b/include/linux/mroute.h
index 7da2cee..35a8277 100644
--- a/include/linux/mroute.h
+++ b/include/linux/mroute.h
@@ -128,6 +128,18 @@
 #ifdef __KERNEL__
 #include <net/sock.h>
 
+#ifdef CONFIG_IP_MROUTE
+static inline int ip_mroute_opt(int opt)
+{
+	return (opt >= MRT_BASE) && (opt <= MRT_BASE + 10);
+}
+#else
+static inline int ip_mroute_opt(int opt)
+{
+	return 0;
+}
+#endif
+
 extern int ip_mroute_setsockopt(struct sock *, int, char __user *, int);
 extern int ip_mroute_getsockopt(struct sock *, int, char __user *, int __user *);
 extern int ipmr_ioctl(struct sock *sk, int cmd, void __user *arg);