Linux PCI driver saves the msi and msix capability offset
in pci_dev->msi_cap and pci_dev->msix_cap. We can use msi_cap
in pci_dev directly, no need hardcode.
Signed-off-by: Du, Changbin <changbin.du@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>