media: imx: imx7-media-csi: Relax width constraints for non-8bpp formats

The driver unconditionally aligns the image width to multiples of 8
pixels. The real alignment constraint is 8 bytes, as indicated by the
CSI_IMAG_PARA.IMAGE_WIDTH documentation that calls for 8 pixel alignment
for 8bpp formats and 4 pixel alignment for other formats.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>