media: rcar-csi2: Enable support for R8A774B1

Add the MIPI CSI-2 driver support for RZ/G2N(R8A774B1) SoC.
The CSI-2 module of RZ/G2N is similar to R-Car M3-N.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
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>