media: imx: imx7-mipi-csis: Align image width based on format

The total number of bits per line needs to be a multiple of 8, which
requires aligning the image width based on the format width. The
csis_pix_format structure contains a pix_width_alignment field that
serves this purpose, but the field is never set. Instead of fixing that,
calculate the alignment constraints based on the bus width for the
format, and drop the unneeded pix_width_alignment field.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>