gpio: rcar: Add R-Car V3U (R8A779A0) support

Add support for the GPIO controller block in the R-Car V3U (R8A779A0)
SoC, which is very similar to the block found on other R-Car Gen3 SoCs.
However, this block has a new General Input Enable Register (INEN),
whose reset state is to have all inputs disabled.

Enable input for all available pins in probe and resume, to support the
use of the General Input Register (INDT) for reading pin state at all
times.  This preserves backwards compatibility with other R-Car Gen3
SoCs, as recommended by the Hardware Manual.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>