media: mediatek: vcodec: Add vdec enable/disable hardware helpers

Lock, power and clock are highly coupled operations. Adds vdec
enable/disable hardware helpers and uses them.

Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
Reviewed-by: Tzung-Bi <Shih&lt;tzungbi@google.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Tested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>