media: mtk-vcodec: Add work queue for core hardware decode

Add work queue to process core hardware information.
First, get lat_buf from message queue, then call core
hardware of each codec(H264/VP9/AV1) to decode, finally
puts lat_buf back to the message.

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>