MdeModulePkg/XhciPei: Support IoMmu.

Update XHCI 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: Star Zeng <star.zeng@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>

MdeModulePkg/Bus/Pci/XhciPei/XhciPei.inf

@@ -37,6 +37,7 @@
   XhcPeim.h
   XhciSched.c
   UsbHcMem.c
+  DmaMem.c
   XhciReg.h
   XhciSched.h
   UsbHcMem.h
@@ -56,6 +57,8 @@
 [Ppis]
   gPeiUsb2HostControllerPpiGuid                 ## PRODUCES
   gPeiUsbControllerPpiGuid                      ## CONSUMES
+  gEdkiiIoMmuPpiGuid                            ## CONSUMES
+  gEfiEndOfPeiSignalPpiGuid                     ## CONSUMES
 
 [Depex]
   gEfiPeiMemoryDiscoveredPpiGuid AND gPeiUsbControllerPpiGuid AND gEfiPeiBootInRecoveryModePpiGuid