media: coda: use correct offset for mpeg4 decoder mvcol buffer

The mvcol buffer needs to be placed behind the chroma plane(s) when
decoding MPEG-4, same as for the h.264 decoder. Use the real offset
with the required rounding.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>