e1_input: Add E1 timeslot number to input_signal_data

It is quite useful for the signal receiver to know on which of the many
E1/T1 timeslots a given event (like a 'link down' event) has happened.
The line number, TEI and SAPI are isnuficcient in case there are
multiple signalling TS in the line.

Change-Id: I07f0f79e0cda09766f357032ffb4e7ad643d448a
4 files changed