vircpi: Add PCIe 5.0 and 6.0 link speeds

vircpi: Add PCIe 5.0 and 6.0 link speeds

The PCIe 5.0 and PCIe 6.0 standards define new link speeds:
32GT/s and 64GT/s, respectively. Update our internal enum to
include these new speeds. Otherwise we format incorrect XML:

  <pci-express>
    <link validity='cap' port='0' speed='(null)' width='16'/>
    <link validity='sta' speed='16' width='16'/>
  </pci-express>

Like all "good" specifications, these are also locked behind a
login portal. But we can look at pciutils' source code: [1] and
[2].

1: https://git.kernel.org/pub/scm/utils/pciutils/pciutils.git/commit/ls-caps.c?id=caca31a0eea41c7b051705704c1158fddc02fbd2
2: https://git.kernel.org/pub/scm/utils/pciutils/pciutils.git/commit/ls-caps.c?id=5bdf63b6b1bc35b59c4b3f47f7ca83ca1868155b

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2105231
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>