arm64: dts: renesas: r8a779h0: Add pinctrl device node

Add a device node for the Pin Function Controller on the Renesas R-Car
V4M (R8A779H0) SoC.

Signed-off-by: Hai Pham <hai.pham.ud@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/0ab32290014b64ddbee5c9ec2808c8294d0b6192.1706266286.git.geert+renesas@glider.be