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/icmp.c b/net/ipv4/icmp.c
index 5e56401..f5203fb 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -399,7 +399,7 @@
 		return;
 
 	sk = icmp_xmit_lock(net);
-	if (sk == NULL)
+	if (!sk)
 		return;
 	inet = inet_sk(sk);
 
@@ -609,7 +609,7 @@
 						 skb_in->data,
 						 sizeof(_inner_type),
 						 &_inner_type);
-			if (itp == NULL)
+			if (!itp)
 				goto out;
 
 			/*
@@ -627,7 +627,7 @@
 		return;
 
 	sk = icmp_xmit_lock(net);
-	if (sk == NULL)
+	if (!sk)
 		goto out_free;
 
 	/*