media: mtk-vcodec: Add to support multi hardware decode

There are more than two hardwares for decoder: LAT0, LAT1 and CORE. In
order to manage these hardwares, register each hardware as independent
platform device for the larbs are different.

Each hardware module controls its own information which includes
interrupt/power/clocks/registers.

Calling of_platform_populate in parent device, and use subdev_bitmap to
record whether the hardwares are registered.

Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
Reviewed-by: Steve Cho <stevecho@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>