MdeModulePkg/PciHostBridge: Add IOMMU support.

MdeModulePkg/PciHostBridge: Add IOMMU support.

If IOMMU protocol is installed, PciHostBridge just calls
IOMMU AllocateBuffer/FreeBuffer/Map/Unmap.

PciHostBridge does not set IOMMU access attribute,
because it does not know which device request the DMA.
This work is done by PciBus driver.

Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Leo Duran <leo.duran@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Previous patch Tested-by: Brijesh Singh <brijesh.singh@amd.com>
Previous patch Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Leo Duran <leo.duran@amd.com>