MdeModulePkg/NvmExpressPei: Avoid updating the module-level variable

This commit is out of the scope for BZ-1409. The commit will remove the
call of RegisterForShadow() at the entry point of the driver. By doing so,
the driver is now possible to be executed without being re-loaded into
permanent memory.

Thus, this commit will update the NvmExpressPei driver to avoid updating
the content of a global variable.

Cc: Jian J Wang <jian.j.wang@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>

MdeModulePkg/Bus/Pci/NvmExpressPei/NvmExpressPei.c

@@ -2,7 +2,7 @@
   The NvmExpressPei driver is used to manage non-volatile memory subsystem
   which follows NVM Express specification at PEI phase.
 
-  Copyright (c) 2018, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2018 - 2019, Intel Corporation. All rights reserved.<BR>
 
   This program and the accompanying materials
   are licensed and made available under the terms and conditions
@@ -214,13 +214,6 @@ NvmExpressPeimEntry (
   PEI_NVME_CONTROLLER_PRIVATE_DATA         *Private;
   EFI_PHYSICAL_ADDRESS                     DeviceAddress;
 
-  //
-  // Shadow this PEIM to run from memory
-  //
-  if (!EFI_ERROR (PeiServicesRegisterForShadow (FileHandle))) {
-    return EFI_SUCCESS;
-  }
-
   //
   // Locate the NVME host controller PPI
   //
@@ -235,8 +228,6 @@ NvmExpressPeimEntry (
     return EFI_UNSUPPORTED;
   }
 
-  IoMmuInit ();
-
   Controller = 0;
   MmioBase   = 0;
   while (TRUE) {