PCI: break MSI-X data out of struct pci_dev_info

PCI: break MSI-X data out of struct pci_dev_info

Considering that a significant share of PCI devices out there (not the
least the myriad of CPU-exposed ones) don't support MSI-X at all, and
that the amount of data is well beyond a handful of bytes, break this
out of the common structure, at once allowing the actual data to be
tracked to become architecture specific.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>