PCI: don't say we claimed a resource if we failed

pci_claim_resource() can fail, so pay attention and only claim success
when it actually succeeded.  If pci_claim_resource() fails, it prints a
useful diagnostic.

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