media: imx: capture: refactor enum_/try_fmt

By checking and handling the internal IPU formats (ARGB or AYUV) first,
we don't need to check whether it's a bayer format, as we can default to
passing the input format on in all other cases.

This simplifies handling the different configurations for RGB565 between
parallel and MIPI CSI-2, as we don't need to check the details of the
format anymore.

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