media: mediatek: vcodec: using decoder status instead of core work count

Adding the definition of decoder status to separate different decoder
period for core hardware.

core_work_cnt is the number of core work queued to work queue, the control
is very complex, leading to some unreasonable test result.

Using parameter status to indicate whether queue core work to work queue.

Fixes: 2e0ef56d ("media: mediatek: vcodec: making sure queue_work successfully")
Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>