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>