ArmVirtualizationPkg/PciHostBridgeDxe: IO space is emulated with MMIO
    
    There is no IO space on ARM, and there are no special instructions that
    access it. QEMU emulates the IO space for PCI devices with a special MMIO
    range. We're ready to use it at this point, we just have to switch the
    Io(Read|Write)(8|16|32) primitives to their MMIO counterparts, because in
    "MdePkg/Library/BaseIoLibIntrinsic/IoLibArm.c", the IO primitives
    correctly ASSERT (FALSE).
    
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>