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/ping.c

@@ -516,7 +516,7 @@ void ping_err(struct sk_buff *skb, int offset, u32 info)
 		 ntohs(icmph->un.echo.sequence));
 
 	sk = ping_lookup(net, skb, ntohs(icmph->un.echo.id));
-	if (sk == NULL) {
+	if (!sk) {
 		pr_debug("no socket, dropping\n");
 		return;	/* No socket for error */
 	}