drm/mediatek: remove cast to pointers passed to kfree

drm/mediatek: remove cast to pointers passed to kfree

[ Upstream commit 854d55820cdf19b167dd910446d950b5d0eeadef ]

Remove unnecessary casts to pointer types passed to kfree.
Issue detected by coccinelle:
@@
type t1;
expression *e;
@@

-kfree((t1 *)e);
+kfree(e);

Signed-off-by: Wambui Karuga <wambui.karugax@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20191023111107.9972-1-wambui.karugax@gmail.com
Stable-dep-of: 4744cde06f57 ("drm/mediatek: Use NULL instead of 0 for NULL pointer")
Signed-off-by: Sasha Levin <sashal@kernel.org>