TRX init fixes and reopen function

[mattwire]

Hallo,

I am using rfxtrx with ser2net and have been debugging some reconnection/reinitialisation issues.  I attach a patch with the following fixes/changes:
1. Add "reopen" set function.
2. Fix typo in Ready function (OpenDev should call DoInit not Ready).
3. Modify DoInit / Clear for robustness.

[Willi]

Thanks a lot for this patch! 

I have applied it to SVN some minutes ago.