#179 maxNumRetries in tlm_request() are not limited

[Michael Anderegg]

The maximum retries of a request must be in range of 0..2 appropriate to IEC 61375-2-3 A.19.
The function tlm_request() has only a limitation in comment but no hook in code. The user can even add more retries than specified in the norm and the stack retries as submitted.
Please add a hook to the code and return for example a parameter error if the submitted maxNumRetries exceed 2 retries.

[Armin-Hagen Weiss]

Retries were defined double in tlm_request(). Single parameter maxNumRetries removed and pSendParam->retries used.