PCI: iproc: Call pci_fixup_irqs() for ARM64 as well as ARM

After 459a0772 ("PCI: Build setup-irq.o for arm64"), we build
setup-irq.o for arm64, so we can use pci_fixup_irqs() on both arm and
arm64.

Remove the "#ifdef CONFIG_ARM" around the call to pci_fixup_irqs().

[bhelgaas: changelog]
Signed-off-by: Ray Jui <rjui@broadcom.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>