pinctrl: renesas: Initial R8A779F0 PFC support

Add initial Pin Function Controller (PFC) support for the Renesas R-Car
S4-8 (R8A779F0) SoC, including bias, drive strength and voltage control.

Based on a larger patch in the BSP by LUU HOAI.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/fd8201da404b7b0897130b254380ffc97f437266.1645457792.git.geert+renesas@glider.be