OvmfPkg/PciHotPlugInitDxe: translate QEMU's resource reservation hints

OvmfPkg/PciHotPlugInitDxe: translate QEMU's resource reservation hints

Parse QEMU_PCI_BRIDGE_CAPABILITY_RESOURCE_RESERVATION from the bridges'
conventional config spaces. Translate the fields as follows:

* BusNumbers:
  * 0 -- no reservation;
  * (-1) -- firmware default, i.e. no reservation;
  * otherwise -- reserve the requested value. (NB, bus number reservation
    is not supposed to work before
    <https://bugzilla.tianocore.org/show_bug.cgi?id=656> is fixed.)

* Io:
  * 0 -- no reservation;
  * (-1) -- keep our current default (512B);
  * otherwise -- round up the requested value and reserve that.

* NonPrefetchable32BitMmio:
  * 0 -- no reservation;
  * (-1) -- keep our current default (2MB);
  * otherwise -- round up the requested value and reserve that.

* Prefetchable32BitMmio:
  * 0 -- no reservation, proceed to Prefetchable64BitMmio;
  * (-1) -- firmware default, i.e. no reservation, proceed to
    Prefetchable64BitMmio;
  * otherwise -- round up the requested value and reserve that. (NB, if
    Prefetchable32BitMmio is reserved in addition to
    NonPrefetchable32BitMmio, then PciBusDxe currently runs into an
    assertion failure. Refer to
    <https://bugzilla.tianocore.org/show_bug.cgi?id=720>.)

* Prefetchable64BitMmio:
  * only reached if Prefetchable32BitMmio was not reserved;
  * 0 -- no reservation;
  * (-1) -- firmware default, i.e. no reservation;
  * otherwise -- round up the requested value and reserve that.

If QEMU_PCI_BRIDGE_CAPABILITY_RESOURCE_RESERVATION is missing, plus any
time the rounding fails, fall back to the current defaults.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Marcel Apfelbaum <marcel@redhat.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>