evdev: Replace rcu_assign_pointer() with RCU_INIT_POINTER()

The use of "rcu_assign_pointer()" is NULLing out the pointer. According to RCU_INIT_POINTER()'s block comment:
"1. This use of RCU_INIT_POINTER() is NULLing out the pointer"
it is better to use it instead of rcu_assign_pointer() because it has a smaller overhead.

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

- rcu_assign_pointer
+ RCU_INIT_POINTER
(..., NULL)

---
 drivers/input/evdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index fd325ec..33e53a7 100644
@@ -291,7 +291,7 @@ static int evdev_ungrab(struct evdev *evdev, struct evdev_client *client)
 	if (grab != client)
 		return  -EINVAL;
 
-	rcu_assign_pointer(evdev->grab, NULL);
+	RCU_INIT_POINTER(evdev->grab, NULL);
 	synchronize_rcu();
 	input_release_device(&evdev->handle);
 

1.9.1

Hi Andreea,

The same objection as here: https://lkml.org/lkml/2014/3/23/96

Thanks.

Dmitry