Fix pci_claim_resource

Instead of starting from the iomem or ioport roots, start from the
parent bus' resources.  This fixes a bug where child resources would
appear above their parents resources if they had the same size.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Tested-by: Andrew Patterson <andrew.patterson@hp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>