ipv4: coding style: comparison for equality with NULL

The ipv4 code uses a mixture of coding styles. In some instances check
for NULL pointer is done as x == NULL and sometimes as !x. !x is
preferred according to checkpatch and this patch makes the code
consistent by adopting the latter form.

No changes detected by objdiff.

Signed-off-by: Ian Morris <ipm@chirality.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 4bb7252..31eaa9b 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -654,7 +654,7 @@
 	if (dst == 0) {
 		/* NBMA tunnel */
 
-		if (skb_dst(skb) == NULL) {
+		if (!skb_dst(skb)) {
 			dev->stats.tx_fifo_errors++;
 			goto tx_error;
 		}
@@ -672,7 +672,7 @@
 
 			neigh = dst_neigh_lookup(skb_dst(skb),
 						 &ipv6_hdr(skb)->daddr);
-			if (neigh == NULL)
+			if (!neigh)
 				goto tx_error;
 
 			addr6 = (const struct in6_addr *)&neigh->primary_key;
@@ -843,7 +843,7 @@
 	case SIOCGETTUNNEL:
 		if (dev == itn->fb_tunnel_dev) {
 			t = ip_tunnel_find(itn, p, itn->fb_tunnel_dev->type);
-			if (t == NULL)
+			if (!t)
 				t = netdev_priv(dev);
 		}
 		memcpy(p, &t->parms, sizeof(*p));
@@ -914,7 +914,7 @@
 		if (dev == itn->fb_tunnel_dev) {
 			err = -ENOENT;
 			t = ip_tunnel_find(itn, p, itn->fb_tunnel_dev->type);
-			if (t == NULL)
+			if (!t)
 				goto done;
 			err = -EPERM;
 			if (t == netdev_priv(itn->fb_tunnel_dev))