media: rcar-vin: Use generic parser for parsing fwnode endpoints

Instead of using a custom driver implementation, use
v4l2_async_notifier_parse_fwnode_endpoints() to parse the fwnode endpoints
of the device.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>