PCI: Move resource distribution for single bridge outside loop

If there is only a single bridge on the bus, we assign all resources to it.
Currently this is done as a part of the resource distribution loop but it
does not have to be there, and moving it outside actually improves
readability because we can then save one indent level in the loop.

While there we can add hotplug_bridges == 1 && normal_bridges == 0 to
the same block because they are dealt the same way.

Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>