This is a follow-on to 'vPCI: avoid bogus "overlap in extended cap list"
warnings', addressing further issues noted there.

v4: Three new patches and some other re-work. See individual patches.

1: x86/PCI: avoid re-evaluation of extended config space accessibility
2: vPCI: introduce private header
3: vPCI: move vpci_init_capabilities() to a separate file
4: vPCI: move capability-list init
5: vPCI: re-init extended-capabilities when MMCFG availability changed

Jan