media: mediatek: vcodec: Get each context resolution information

Will store the string to temp buffer like "echo -picinfo > vdec" when
user want to get needed information.

Then getting debug information using command 'cat vdec' calling
mtk_vdec_dbgfs_read to analysis the temp buffer.

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>