net/openvswitch/flow.c: Replace rcu_dereference() with rcu_access_pointer()

The "rcu_dereference()" call is used directly in a condition.
Since its return value is never dereferenced it is recommended to use
"rcu_access_pointer()" instead of "rcu_dereference()".
Therefore, this patch makes the replacement.

The following Coccinelle semantic patch was used:
@@
@@

(
 if(
 (<+...
- rcu_dereference
+ rcu_access_pointer
  (...)
  ...+>)) {...}
|
 while(
 (<+...
- rcu_dereference
+ rcu_access_pointer
  (...)
  ...+>)) {...}
)
Signed-off-by: Andreea-Cristina Bernat <bernat.ada@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/flow.c

@@ -89,7 +89,7 @@ void ovs_flow_stats_update(struct sw_flow *flow, __be16 tcp_flags,
 			 * allocated stats as we have already locked them.
 			 */
 			if (likely(flow->stats_last_writer != NUMA_NO_NODE)
-			    && likely(!rcu_dereference(flow->stats[node]))) {
+			    && likely(!rcu_access_pointer(flow->stats[node]))) {
 				/* Try to allocate node-specific stats. */
 				struct flow_stats *new_stats;