ipv6: coding style: comparison for equality with NULL

The ipv6 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/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index bc28b7d..aa9ea6e 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -395,7 +395,7 @@
 				flags & GRE_KEY ?
 				*(((__be32 *)p) + (grehlen / 4) - 1) : 0,
 				p[1]);
-	if (t == NULL)
+	if (!t)
 		return;
 
 	switch (type) {
@@ -980,7 +980,7 @@
 						 &p->raddr, &p->laddr,
 						 p->link, strict);
 
-		if (rt == NULL)
+		if (!rt)
 			return;
 
 		if (rt->dst.dev) {
@@ -1073,7 +1073,7 @@
 			}
 			ip6gre_tnl_parm_from_user(&p1, &p);
 			t = ip6gre_tunnel_locate(net, &p1, 0);
-			if (t == NULL)
+			if (!t)
 				t = netdev_priv(dev);
 		}
 		memset(&p, 0, sizeof(p));
@@ -1144,7 +1144,7 @@
 			err = -ENOENT;
 			ip6gre_tnl_parm_from_user(&p1, &p);
 			t = ip6gre_tunnel_locate(net, &p1, 0);
-			if (t == NULL)
+			if (!t)
 				goto done;
 			err = -EPERM;
 			if (t == netdev_priv(ign->fb_tunnel_dev))