MdeModulePkg/SmmCore: SMM register protocol notify function clarify

PI 1.4 clarified SMM register protocol notify function return status as below:
EFI_SUCCESS           Successfully returned the registration record that has
                      been added or unhooked
EFI_INVALID_PARAMETER Protocol is NULL or Registration is NULL
The implementation of SmmRegisterProtocolNotify() already followed this new
rule, needn't to be updated.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17349 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Core/PiSmmCore/Notify.c

@@ -1,7 +1,7 @@
 /** @file
   Support functions for UEFI protocol notification infrastructure.
 
-  Copyright (c) 2009 - 2013, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2009 - 2015, Intel Corporation. All rights reserved.<BR>
   This program and the accompanying materials are licensed and made available 
   under the terms and conditions of the BSD License which accompanies this 
   distribution.  The full text of the license may be found at        
@@ -91,9 +91,9 @@ SmmRemoveInterfaceFromProtocol (
   @param  Function               Points to the notification function
   @param  Registration           Returns the registration record
 
-  @retval EFI_INVALID_PARAMETER  Invalid parameter
   @retval EFI_SUCCESS            Successfully returned the registration record
-                                 that has been added
+                                 that has been added or unhooked
+  @retval EFI_INVALID_PARAMETER  Protocol is NULL or Registration is NULL
   @retval EFI_OUT_OF_RESOURCES   Not enough memory resource to finish the request
   @retval EFI_NOT_FOUND          If the registration is not found when Function == NULL