arm64: dts: renesas: r8a77980: Add RPC-IF support

Describe RPC-IF in the R8A77980 device tree.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>

Link: https://lore.kernel.org/r/f18853d9-8ef9-717a-9039-2191b26e579f@cogentembedded.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>