PCI: add PCI_MSIX_TABLE/PBA defines

These are already defined in pcilib's pci/header.h but not in kernel's
linux/pci_regs.h.  Copy them to avoid using magic numbers.

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>