Input: remove unnecessary synchronize_rcu() call

There is no need to issue serialize_rcu() after adding a new handle
to the list of handles associated with the device because new events
will "see" the new handle in the list immediately. Remove it so we
can boot a little bit faster.
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/input.c

@@ -1551,7 +1551,6 @@ int input_register_handle(struct input_handle *handle)
 		return error;
 	list_add_tail_rcu(&handle->d_node, &dev->h_list);
 	mutex_unlock(&dev->mutex);
-	synchronize_rcu();
 
 	/*
 	 * Since we are supposed to be called from ->connect()