irqchip/irq-csky-mpintc: Add triger type

Support 4 triger types:
 - IRQ_TYPE_LEVEL_HIGH
 - IRQ_TYPE_LEVEL_LOW
 - IRQ_TYPE_EDGE_RISING
 - IRQ_TYPE_EDGE_FALLING

All of above could be set in DeviceTree file and it still compatible
with the old DeviceTree format.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>