MdeModulePkg: Replace unsafe string functions.

Replace unsafe string functions with new added safe string functions.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Zhang Lubo <lubo.zhang@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17881 6f19259b-4bc3-4df7-8a09-765794883524

MdeModulePkg/Library/DxeNetLib/DxeNetLib.c

@@ -3230,7 +3230,7 @@ NetLibIp6ToStr (
     return EFI_BUFFER_TOO_SMALL;
   }
 
-  StrCpy (String, Buffer);
+  StrCpyS (String, StringSize / sizeof (CHAR16), Buffer);
 
   return EFI_SUCCESS;
 }