MdeModulePkg/PciBusDxe: don't create bogus descriptor if no resources needed

MdeModulePkg/PciBusDxe: don't create bogus descriptor if no resources needed

If the current PCI configuration requires no resources to be allocated at
all (i.e., unpopulated bus), the PCI enumeration code creates a single
ACPI_ADDRESS_SPACE_DESCRIPTOR memory descriptor with all fields cleared.
This is rejected by the SubmitResources() implementation of the generic
PciHostBridgeDxe in the following way:

  PciHostBridge: SubmitResources for PcieRoot(0x0)
   Mem: Granularity/SpecificFlag = 0 / 00
        Length/Alignment = 0x0 / 0x0
  PciBus: HostBridge->SubmitResources() - Invalid Parameter

  ASSERT_EFI_ERROR (Status = Invalid Parameter)
  ASSERT [PciBusDxe] .../PciBusDxe/PciLib.c(561): !EFI_ERROR (Status)

So instead, create the empty configuration as a single entry of type
EFI_ACPI_END_TAG_DESCRIPTOR.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>