PCI: xilinx: Don't call pci_fixup_irqs() on Microblaze

The Xilinx AXI PCIe Host Bridge Soft IP driver was previously only
supported on ARM (in particular, on ARCH_ZYNC), and pci_fixup_irqs() is
available there.  But Microblaze will do IRQ fixup in pcibios_add_device(),
so pci_fixup_irqs() is not available on Microblaze.

Don't call pci_fixup_irqs() on Microblaze, so the driver can work on both
Zynq and Microblaze Architectures.

[bhelgaas: revise changelog to show similarity to bdb8a184 ("PCI: iproc: Call pci_fixup_irqs() for ARM64 as well as ARM")]
Signed-off-by: Bharat Kumar Gogada <bharatku@xilinx.com>
Signed-off-by: Ravi Kiran Gummaluri <rgummal@xilinx.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Michal Simek <michal.simek@xilinx.com>