BugID: 972

Overload two unused bits for administration purposes TDBoardStatus.

Relevant comment in code:
//
// The unkown and invalid bits have no meaning in the TD status byte.
// They are overloaded here to indicate whether the value stored has
// been read from hardware and whether the RSP board has control over
// the TD board:
//
// unknown: (0 = value has been read from hardware, 1 = value has not been read)
// invalid: (0 = RSP board is controlling a TD board, 1 = RSP board is not controlling a TD board)
//