pinctrl: renesas: Initial R8A779H0 (R-Car V4M) PFC support

Add initial pin control support for the R-Car V4M (R8A779H0) SoC,
including bias, drive strength and voltage control.

Signed-off-by: Cong Dang <cong.dang.xn@renesas.com>
[geert: Fixes and cleanups]
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/5f59263e75be713dc954007cfeb2c99274c9d761.1706264667.git.geert+renesas@glider.be