media: mediatek: vcodec: move lat_buf to the top of core list

Current instance will decode done when begin to wait lat buf full,
move the lat_buf of current instance to the top of core list to make
sure current instance's lat_buf will be used firstly.

Fixes: 365e4ba0

 ("media: mtk-vcodec: Add work queue for core hardware decode")
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>