dt-bindings: gpio: renesas,rcar-gpio: Add r8a779h0 support

Document support for GPIO controller blocks in the Renesas R-Car V4M
(R8A779H0) SoC.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>