The MIPS based xilfpga platform has the following IRQ structure

Peripherals --> xilinx_intcontroller -> mips_cpu_int controller

Add support for the driver to chain the irq handler
Signed-off-by: NZubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>