measurement.c: Fix sdcch4_meas_rep_fn102 / sdcch8_meas_rep_fn102
measurement.c: Fix sdcch4_meas_rep_fn102 / sdcch8_meas_rep_fn102

Since Change-Id: I23fba50f48415314da40cf5bf86fce2ed3e66af6 we were not
reporting measurements for SDCCH channel types due to the wrong
encoding of the sdcch{4,8}_meas_rep_fn102 table.

Let's fix the table by encoding the needed information:

 "What is the modulo-102 remainder of the first burst of the last block
  before fn%102 reaches 37?" (SDCCH/4)

 "What is the modulo-102 remainder of the first burst of the last block
  before fn%102 reaches 12?" (SDCCH/8)

The TS 45.002 Clause 7 tables have to be consulted carefully to
determine this information.

Change-Id: Icf02354872670126ab3297b787b216981ca6c309
Related: OS#2965

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts