[media] mx2_camera: Fix sizeimage computation in try_fmt()

The try_fmt() handler restricts the image width based on the hardware
limits and updates the bytesperline value, but doesn't update sizeimage.
Fix it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>