pinctrl: sh-pfc: r8a77980: Add RPC pins, groups, and functions

Add the RPC pins/groups/functions to the R8A77980 PFC driver.
They can be used if an Octal-SPI flash or HyperFlash is connected.

Based on the patch by Dmitry Shifrin <dmitry.shifrin@cogentembedded.com>.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Link: https://lore.kernel.org/r/fd089d37-95bb-4ec9-282f-e04d7e5195e4@cogentembedded.com


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