PCI: break out primary/secondary/subordinate for readability

No functional change; just add names for the primary/secondary/subordinate
bus numbers read from config space rather than repeatedly masking/shifting.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
1 file changed