drm: minor kref_put() nits

There's no need to pass kref_put() the address of a function (just the
function will do just fine) nor to cast its unused return to void.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/gpu/drm/radeon/radeon_fence.c b/drivers/gpu/drm/radeon/radeon_fence.c
index 9e59868..ab83472 100644
--- a/drivers/gpu/drm/radeon/radeon_fence.c
+++ b/drivers/gpu/drm/radeon/radeon_fence.c
@@ -322,7 +322,7 @@
 
 	*fence = NULL;
 	if (tmp) {
-		kref_put(&tmp->kref, &radeon_fence_destroy);
+		kref_put(&tmp->kref, radeon_fence_destroy);
 	}
 }