gpio: renesas: Add R-Car Gen4 support

Add support for the GPIO controller block in the R-Car Gen4 family.

It has a General Input Enable Register (INEN), whose reset state is to
have all inputs disabled.

Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Signed-off-by: Hai Pham <hai.pham.ud@renesas.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>