MIPS: xilfpga: Use Xilinx Interrupt Controller

MIPS: xilfpga: Use Xilinx Interrupt Controller

IRQs from peripherals such as i2c/uart/ethernet come via
the AXI Interrupt controller.

Select it in Kconfig for xilfpga and add the DT node

Signed-off-by: Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14592/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>