media: rcar-vin: convert to SPDX identifiers

Kconfig and Makefile doesn't have license line, thus,
these are GPL-2.0 as default.
All ohter files are GPL-2.0+ as original license.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>