openvswitch: Use IS_ERR_OR_NULL

This patch introduces the use of the macro IS_ERR_OR_NULL in place of
tests for NULL and IS_ERR.

The following Coccinelle semantic patch was used for making the change:

@@
expression e;
@@

- e == NULL || IS_ERR(e)
+ IS_ERR_OR_NULL(e)
 || ...
Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/datapath.c

@@ -781,7 +781,7 @@ static struct sk_buff *ovs_flow_cmd_build_info(const struct sw_flow *flow,
 
 	skb = ovs_flow_cmd_alloc_info(ovsl_dereference(flow->sf_acts), info,
 				      always);
-	if (!skb || IS_ERR(skb))
+	if (IS_ERR_OR_NULL(skb))
 		return skb;
 
 	retval = ovs_flow_cmd_fill_info(flow, dp_ifindex, skb,