datapath: Use with RCU_INIT_POINTER(x, NULL) in vport-gre.c

This patch replaces rcu_assign_pointer(x, NULL) with RCU_INIT_POINTER(x, NULL)

The rcu_assign_pointer() ensures that the initialization of a structure
is carried out before storing a pointer to that structure.
And in the case of the NULL pointer, there is no structure to initialize.
So, rcu_assign_pointer(p, NULL) can be safely converted to RCU_INIT_POINTER(p, NULL)

Signed-off-by: Monam Agarwal <[email protected]>
Signed-off-by: Jesse Gross <[email protected]>

datapath/vport-gre.c

@@ -257,7 +257,7 @@ static void gre_tnl_destroy(struct vport *vport)
 
 	ovs_net = net_generic(net, ovs_net_id);
 
-	rcu_assign_pointer(ovs_net->vport_net.gre_vport, NULL);
+	RCU_INIT_POINTER(ovs_net->vport_net.gre_vport, NULL);
 	ovs_vport_deferred_free(vport);
 	gre_exit();
 }