OvmfPkg/PlatformPei: provide 10 * 4KB of PCI IO Port space on Q35

OvmfPkg/PlatformPei: provide 10 * 4KB of PCI IO Port space on Q35

This can accommodate 10 bridges (including root bridges, PCIe upstream and
downstream ports, etc -- see
<https://bugzilla.redhat.com/show_bug.cgi?id=1333238#c12> for more
details).

10 is not a whole lot, but closer to the architectural limit of 15 than
our current 4, so it can be considered a stop-gap solution until all
guests manage to migrate to virtio-1.0, and no longer need PCI IO BARs
behind PCIe downstream ports.

Cc: Gabriel Somlo <somlo@cmu.edu>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1333238
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Tested-by: Gabriel Somlo <somlo@cmu.edu>