Add function to make Uplink Measurement

It assembles RSL Uplink Measurement IE according to 3GPP TS 08.58
ยง9.3.25. The function is based on lchan_build_rsl_ul_meas() from OsmoBTS
but optionally includes DTX information.

Change-Id: Ib37107bcc9909e5105ea711de42d3fb1db7e8d9e
Reviewed-on: https://gerrit.osmocom.org/44
Tested-by: Jenkins Builder
Reviewed-by: Harald Welte <laforge@gnumonks.org>
3 files changed