media: mtk-vcodec: enlarge struct vdec_pic_info fields

Enlarge the plane number to support more complex case
and add the support for fmt change case.

Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>