[NET] NETNS: Omit namespace comparision without CONFIG_NET_NS.

Introduce an inline net_eq() to compare two namespaces.
Without CONFIG_NET_NS, since no namespace other than &init_net
exists, it is always 1.

We do not need to convert 1) inline vs inline and
2) inline vs &init_net comparisons.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
diff --git a/net/core/dev.c b/net/core/dev.c
index 8125348..75c3f7f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4136,7 +4136,7 @@
 
 	/* Get out if there is nothing todo */
 	err = 0;
-	if (dev_net(dev) == net)
+	if (net_eq(dev_net(dev), net))
 		goto out;
 
 	/* Pick the destination device name, and ensure