MdeModulePkg/SdBlockIoPei: Support IoMmu

Update the SdBlockIoPei driver to consume IOMMU_PPI to allocate DMA
buffer.

If no IOMMU_PPI exists, this driver still calls PEI service
to allocate DMA buffer, with assumption that DRAM==DMA.

This is a compatible change.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>

MdeModulePkg/Bus/Sd/SdBlockIoPei/SdHcMem.h

@@ -1,6 +1,6 @@
 /** @file
 
-Copyright (c) 2015, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2015 - 2017, Intel Corporation. All rights reserved.<BR>
 
 This program and the accompanying materials
 are licensed and made available under the terms and conditions
@@ -27,7 +27,9 @@ struct _SD_PEIM_MEM_BLOCK {
   UINT8                   *Bits;    // Bit array to record which unit is allocated
   UINTN                   BitsLen;
   UINT8                   *Buf;
+  UINT8                   *BufHost;
   UINTN                   BufLen;   // Memory size in bytes
+  VOID                    *Mapping;
   SD_PEIM_MEM_BLOCK       *Next;
 };