media: mediatek: vcodec: return EINVAL if plane is too small

Modify vb2ops_vdec_buf_prepare to return EINVAL if the size of the plane
is less than the size of the image. Currently we just log an error and
return 0 anyway, which may cause a buffer overrun bug.

Signed-off-by: Justin Green <greenjustin@chromium.org>
Suggested-by: Andres Calderon Jaramillo <andrescj@chromium.org>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>