media: v4l2-mediabus: Use structures to describe bus configuration

The media bus configuration is specified through a set of flags, some of
which being mutually exclusive. This doesn't scale to express more
complex configurations. Improve the API by replacing the single flags
field in v4l2_mbus_config by a union of v4l2_mbus_config_* structures.
The flags themselves are still used in those structures, so they are
kept here. Drivers are however updated to use structure fields instead
of flags when already possible.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>