osmo_bsc_main.c: verify the physical channel mapping at startup

As per 3GPP TS 45.002, section 3.3.2.3, and table 3 of clause 7,
the following limitations apply mapping of CCCH/BCCH channels:

  - TS0/C0 shall be configured as CCCH/BCCH (optionally combined);
  - combined CCCH (CCCH+SDCCH4) can only be used on TS0;
  - additional CCCHs can be on TS2, TS4, and TS6;
  - additional CCCHs are not allowed if TS0 is combined.

Let's make sure that OsmoBSC is properly configured before starring.

Change-Id: I758ef80f7884ba35cdf59d671ee30222ffb9d68b
3 files changed