ArmVirtPkg/ArmVirtQemu: switch to generic PciHostBridgeDxe

ArmVirtPkg/ArmVirtQemu: switch to generic PciHostBridgeDxe

Wire up the FdtPciHostBridgeLib introduced in the previous patch
to the generic PciHostBridgeDxe implementation, and drop the special
ArmVirtPkg version. The former's dependency on gEfiCpuIo2ProtocolGuid
is satisfied by adding ArmPciCpuIo2Dxe.inf as well, and adding the PCD
gArmTokenSpaceGuid.PcdPciIoTranslation as a dynamic PCD.

In terms of functionality, no changes are intended.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Ref: https://tianocore.acgmultimedia.com/show_bug.cgi?id=65