Define the generic R8A77970 part of the CAN-FD device node.

Based on the original (and large) patch by Vladimir Barinov.
Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram@bp.renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>