media: v4l2-common: add v4l2_fill_pixfmt_mp_aligned helper

media: v4l2-common: add v4l2_fill_pixfmt_mp_aligned helper

Add a v4l2_fill_pixfmt_mp_aligned helper which allows the user to
specify a custom stride alignment in bytes. This is necessary for
hardware like the Rockchip RGA3, which requires the stride value to be
aligned to a 16 bytes boundary.

The code makes some assumptions about the v4l2 format to simplify the
calculation. They currently hold for all known v4l2 formats.

v4l2_format_plane_stride uses an unsigned int as argument type to avoid
the later multiplication from overflowing the u8 value. All other places
use u8, as no practical use cases for a larger alignment are known at
the moment.

Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Sven Püschel <s.pueschel@pengutronix.de>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>