PCI: Simplify pci_bus_distribute_available_resources()

Reorder pci_bus_distribute_available_resources() to group related code
together.  No functional change intended.

Link: https://lore.kernel.org/r/PS2P216MB0642C7A485649D2D787A1C6F80000@PS2P216MB0642.KORP216.PROD.OUTLOOK.COM
Link: https://lore.kernel.org/r/20190622210310.180905-2-helgaas@kernel.org


Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>