media: imx: add support for RGB565_2X8 on parallel bus

The IPU can only capture RGB565 with two 8-bit cycles in bayer/generic
mode on the parallel bus, compared to a specific mode on MIPI CSI-2.
To handle this, we extend imx_media_pixfmt with a cycles per pixel
field, which is used for generic formats on the parallel bus.

Based on the selected format and bus, we then update the width to
account for the multiple cycles per pixel.

Signed-off-by: Jan Luebbe <jlu@pengutronix.de>
Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>