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>

net/ipv4/ipcomp.c

@@ -63,7 +63,7 @@ static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
 	struct xfrm_state *t;
 
 	t = xfrm_state_alloc(net);
-	if (t == NULL)
+	if (!t)
 		goto out;
 
 	t->id.proto = IPPROTO_IPIP;