irqchip/xilinx: Do not call irq_set_default_host()

Using a default domain on DT based platforms is unnecessary.

Signed-off-by: Mubin Sayyed <mubin.usman.sayyed@xilinx.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200317125600.15913-5-mubin.usman.sayyed@xilinx.com