[media] v4l: of: Drop endpoint node reference in v4l2_of_get_remote_port()

The v4l2_of_get_remote_port() function acquires a reference to an
endpoint node through a phandle and then returns the node's parent,
without dropping the reference to the endpoint node. Fix it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>