media: rcar_drif: Remove useless license text when SPDX-License-Identifier is already used

An SPDX-License-Identifier is already in place. There is no need to
duplicate part of the corresponding license.

This is a left-over from commit adeb6970 ("media: rcar_drif: convert to
SPDX identifiers")

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>