meas: lchan_meas_sub_num_expected(): proper cmode enforcement

3GPP TS 45.008, section 8.3 defines TDMA Fn subsets, which shall
always be transmitted when DTX is employed, only for:

* TCH/F in signalling mode (but not for TCH/H),
* TCH/H and TCH/F in data mode (CSD) [*],
* TCH/FS, TCH/EFS, and TCH/HS.

For channel modes employing AMR codec, in particular:

* TCH/AFS, TCH/WFS, O-TCH/WFS,
* TCH/AHS, O-TCH/AHS, O-TCH/WHS,

there exist no fixed TDMA Fn subsets, but DTX is still permitted.
For those we expect at least one SACCH frame, plus a variable
number of speech frames (0 or more).

[*] Handling of data modes is fixed in a follow-up patch.

Change-Id: Ied477528d77871dd7e3b5b7b433a4e33bca40011
Related: OS#6168
---
M src/common/measurement.c
M tests/meas/meas_test.err
2 files changed, 764 insertions(+), 747 deletions(-)