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/ipconfig.c b/net/ipv4/ipconfig.c
index b26376e..8e7328c 100644
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -504,7 +504,8 @@
 	if (!net_eq(dev_net(dev), &init_net))
 		goto drop;
 
-	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
+	skb = skb_share_check(skb, GFP_ATOMIC);
+	if (!skb)
 		return NET_RX_DROP;
 
 	if (!pskb_may_pull(skb, sizeof(struct arphdr)))
@@ -958,7 +959,8 @@
 	if (skb->pkt_type == PACKET_OTHERHOST)
 		goto drop;
 
-	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
+	skb = skb_share_check(skb, GFP_ATOMIC);
+	if (!skb)
 		return NET_RX_DROP;
 
 	if (!pskb_may_pull(skb,