measurement: move SACCH detection to process_l1sap_meas_data()

SACCH detection can be simplified by checking the RSL Link ID in
process_l1sap_meas_data().  This eliminates the need to lookup
the multiframe position by calling trx_sched_is_sacch_fn(), which
definitely takes more CPU time than just L1SAP_IS_LINK_SACCH().

Calling trx_sched_is_sacch_fn() is still required for BTS models
reporting the measurements via PRIM_MPH_INFO (legacy way),
separately from the related Uplink blocks.

This patch can be summarized as follows:

* detect SACCH and set .is_sub=1 in process_l1sap_meas_data();
** for PRIM_MPH_INFO use trx_sched_is_sacch_fn();
** for PRIM_PH_DATA use L1SAP_IS_LINK_SACCH();
* do not call trx_sched_is_sacch_fn() from ts45008_83_is_sub();
* modify the unit test - test_ts45008_83_is_sub_single();
** remove test_ts45008_83_is_sub_is_sacch().

Change-Id: I507e96ee34ac0f8b7a2a6f16a8c7f92bc467df60
Related: SYS#5853
---
M src/common/l1sap.c
M src/common/measurement.c
M tests/meas/meas_test.c
3 files changed, 16 insertions(+), 46 deletions(-)