ipv4: fix NULL checking in devinet_ioctl()

The NULL pointer check `!ifa' should come before its first use.

[ Bug origin : commit fd23c3b3
  (ipv4: Add hash table of interface addresses) in linux-2.6.39 ]
Signed-off-by: NXi Wang <xi.wang@gmail.com>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/devinet.c

@@ -823,9 +823,9 @@ int devinet_ioctl(struct net *net, unsigned int cmd, void __user *arg)
 		if (!ifa) {
 			ret = -ENOBUFS;
 			ifa = inet_alloc_ifa();
-			INIT_HLIST_NODE(&ifa->hash);
 			if (!ifa)
 				break;
+			INIT_HLIST_NODE(&ifa->hash);
 			if (colon)
 				memcpy(ifa->ifa_label, ifr.ifr_name, IFNAMSIZ);
 			else