irqchip/meson-gpio: Rework meson irqchip driver to support meson-A1 SoCs

Since Meson-A1 SoCs register layout of gpio interrupt controller has
difference with previous chips, registers to decide irq line and offset
of trigger method are all changed, the current driver should be modified.

Signed-off-by: Qianggui Song <qianggui.song@amlogic.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20191216123645.10099-3-qianggui.song@amlogic.com