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>
2 files changed