irqchip/xilinx: Remove microblaze+zynq dependency

The Xilinx IRQ controller doesn't really have any architecture
dependencies - it's a generic AXI component that can be used for any
FPGA core from Zynq hard processor systems to microblaze+riscv soft
cores and more.

Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Acked-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220606213952.298686-1-jamie@jamieiles.com