MFC: r223984

MFC: r223984

PCIB_ALLOC_MSIX() may already fail on the first pass, f.e. when the PCI-PCI
bridge is blacklisted. In that case just return from pci_alloc_msix_method(),
otherwise we continue without a single MSI-X resource, causing subsequent
attempts to use the seemingly available resource to fail or when booting
verbose to NULL-dereference rle->start when trying to print the IRQ in
pci_alloc_msix_method().

Reviewed by:	jhb

git-svn-id: svn://svn.freebsd.org/base/stable/8@224394 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f