[media] coda: correctly set capture compose rectangle

Correctly store the rectangle of valid video data in the destination
q_data before rounding up to macroblock size. This fixes the output
of VIDIOC_G_SELECTION for the capture side compose rectangle.

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