media: v4l: fwnode: Detect bus type correctly

In case the device supports multiple video bus types on an endpoint, the
V4L2 fwnode framework attempts to detect the type based on the available
information. This wasn't working really well, and sometimes could lead to
the V4L2 fwnode endpoint struct as being mishandled between the bus types.

Default to Bt.656 if no properties suggesting a bus type are found.

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>