pinctrl: sh-pfc: Add R8A77970 PFC support

Add the PFC support for the R8A77970 SoC including pin groups for some
on-chip devices such as CAN-FD, [H]SCIF, I2C, INTC-EX, MMC, MSIOF, PWM,
VIN...

Based on the original (and large) patch by Daisuke Matsushita
<daisuke.matsushita.ns@hitachi.com>.

Signed-off-by: Vladimir Barinov <vladimir.barinov@cogentembedded.com>
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Rob Herring <robh@kernel.org>
[geert: Drop EtherAVB for now]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>