arm64: dts: renesas: r8a77980: add CAN-FD support

Define the generic R8A77980 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>
[simon: consistently use tabs for indentation]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>