Support for HiSLIP

[smunaut]

Seems at least new Agilent scope support this.

https://en.wikipedia.org/wiki/High_Speed_LAN_Instrument_Protocol

Having a "helper" to easily use it in Oscilloscope driver would be nice.

[azonenberg]

It appears that liblxi supports it to some extent. I haven't looked into the details on how well it's handled (especially WRT nonblocking commands etc), or whether we'd want to do something else.