SecurityPkg/Pkcs7VerifyDxe: Add format check in DB list contents
    
    Add the size check for invalid format detection in AllowedDb,
    RevokedDb and TimeStampDb list contents.
    
    Cc: Chao Zhang <chao.b.zhang@intel.com>
    Contributed-under: TianoCore Contribution Agreement 1.0
    Signed-off-by: Qin Long <qin.long@intel.com>
    Reviewed-by: Chao Zhang <chao.b.zhang@intel.com>