[media] media: soc_camera: rcar_vin: Add preliminary R-Car M2 support

This adds R-Car M2 (R8A7791) VIN support. Both H2 and M2
variants look the same from the driver's point of view,
so use GEN2 id for both.

Signed-off-by: Valentine Barshak <valentine.barshak@cogentembedded.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
[g.liakhovetski@gmx.de: removed changelog from commit message]
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>