[media] soc-camera: Honor user-requested bytesperline and sizeimage

Compute the bytesperline and sizeimage values when trying/setting
formats or when allocating buffers by taking the user-requested values
into account.

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>