SecurityPkg/TcgStorageCoreLib.h: Use ascii instead of unicode.
    
    _FILE_ parameter is an ASCII string. Current implementation used
    as unicode string instead of ascii string. This patch fixed this
    issue.
    
    BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1081
    
    Cc: Hao Wu <hao.a.wu@intel.com>
    Contributed-under: TianoCore Contribution Agreement 1.1
    Signed_off_by: Eric Dong <eric.dong@intel.com>
    Reviewed-by: Hao Wu <hao.a.wu@intel.com>