docs: link to PCI docs from the kbase page
docs: link to PCI docs from the kbase page

While the PCI docs are linked from formatdomain.html, finding those
links is not straightforward. It is good for users to highlight them in
the kbase pages.  The PCI docs are intentionally not moved to the kbase/
sub-directory in order to avoid breaking hyperlinks.

Reviewed-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>
Signed-off-by: Daniel P. Berrangé <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

olafhering/libvirt,nertpinx/libvirt,libvirt/libvirt,zippy2/libvirt,libvirt/libvirt,libvirt/libvirt,nertpinx/libvirt,olafhering/libvirt,jfehlig/libvirt,jfehlig/libvirt,olafhering/libvirt,zippy2/libvirt,nertpinx/libvirt,crobinso/libvirt,zippy2/libvirt,jfehlig/libvirt,zippy2/libvirt,crobinso/libvirt,crobinso/libvirt,nertpinx/libvirt,nertpinx/libvirt,jfehlig/libvirt,crobinso/libvirt,olafhering/libvirt,libvirt/libvirt