media: rcar_drif: Fix fwnode reference leak when parsing DT

The fwnode reference corresponding to the endpoint is leaked in an error
path of the rcar_drif_parse_subdevs() function. Fix it, and reorganize
fwnode reference handling in the function to release references early,
simplifying error paths.

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+huawei@kernel.org>