pinctrl: sh-pfc: Add R8A77980 PFC support

Add the PFC support for the R8A77980 SoC including pin groups for some
on-chip devices such as AVB, CAN-FD, GETHER, [H]SCIF, I2C, INTC-EX, MMC,
MSIOF, PWM, and VIN...

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>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>