irqchip/irq-imx-gpcv2: Forward irq type to parent

The GPCv2 is a stacked IRQ controller below the ARM GIC. It doesn't
care about the IRQ type itself, but needs to forward the type to the
parent IRQ controller, so this one can be configured correctly.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Marc Zyngier <maz@kernel.org>