PCI: xilinx: Use pci_host_probe() to register host

The xilinx host driver does the same host registration and bus scanning
calls as pci_host_probe, so let's use it instead.

The only difference is pci_assign_unassigned_bus_resources() was called
instead of pci_bus_size_bridges() and pci_bus_assign_resources(). This
should be the same.

Link: https://lore.kernel.org/r/20200522234832.954484-16-robh@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Michal Simek <michal.simek@xilinx.com>