SecurityPkg OpalPasswordDxe: Clean password buffer.

Cc: Feng Tian <feng.tian@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Eric Dong <eric.dong@intel.com>

SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalDriver.c

@@ -240,6 +240,7 @@ OpalDriverPopUpHddPassword (
   }
 
   UnicodeStrToAsciiStrS (Unicode, Ascii, MAX_PASSWORD_SIZE + 1);
+  ZeroMem (Unicode, sizeof (Unicode));
 
   return Ascii;
 }