SecurityPkg: Initailize variable Status before it is consumed.
    
    REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2945
    
    V2: Move "Status = EFI_SUCCESS;" before the EDKII_TCG_PRE_HASH check.
    
    Cc: Jiewen Yao <jiewen.yao@intel.com>
    Cc: Jian J Wang <jian.j.wang@intel.com>
    Cc: Qi Zhang <qi1.zhang@intel.com>
    Cc: Rahul Kumar <rahul1.kumar@intel.com>
    Cc: Laszlo Ersek <lersek@redhat.com>
    Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
    Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
    Message-Id: <20200901005505.1722-1-zhiguang.liu@intel.com>
    Reviewed-by: Laszlo Ersek <lersek@redhat.com>