media: v4l: fwnode: Use V4L2 fwnode endpoint media bus type if set

Use the given media bus type set by the caller. If none is given (i.e. the
mbus type is V4L2_MBUS_UNKNOWN, or 0), fall back to the old behaviour.
This is to obtain the information from the DT or try to guess the bus
type.

-ENXIO is returned if the caller sets the bus type but that does not match
with what's in DT. Also return -ENXIO if bus type detection failed to
separate this from the rest of the errors.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Tested-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Tested-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>