Docs incorrect for LMS_Calibrate

[srcejon]

The docs for LMS_Calibrate says:

* @return  0 on success, (-1) on failure

However, in LMS7002M::CalibrateTx, and elsewhere, errnos are returned as the error values:

 return ReportError(EINVAL, "Tx Calibration: MCU error %i (%s)", status, MCU_BD::MCUStatusMessage(status));

So LMS_Calibrate can return EINVAL on error.

Doc should probably be something like:

* @return  0 on success, (-1 or errno) on failure