irqchip/meson-gpio: add support for Meson8 SoCs

Meson8 uses the same GPIO interrupt controller IP block as the other
Meson SoCs. A total of 134 pins can be spied on, which is the sum of:
- 22 pins on bank GPIOX
- 17 pins on bank GPIOY
- 30 pins on bank GPIODV
- 10 pins on bank GPIOH
- 15 pins on bank GPIOZ
- 7 pins on bank CARD
- 19 pins on bank BOOT
- 14 pins in the AO domain

Acked-by: Kevin Hilman <khilman@baylibre.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>