irqchip: Add UniPhier AIDET irqchip driver

UniPhier SoCs contain AIDET (ARM Interrupt Detector).  This is intended
to provide additional features that are not covered by GIC.  The main
purpose is to provide logic inverter to support low level and falling
edge trigger types for interrupt lines from on-board devices.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>