ms: Move MS information merging to GprsMS

Currently the merging of the meta information (MS class, IMSI) takes
place in gprs_rlcmac_tbf::merge_and_clear_ms(). This makes it
difficult to merge the internal state and does not directly relate to
TBFs anyway.

This commit moves this into a new method GprsMs::merge_old_ms.

Sponsored-by: On-Waves ehf
5 files changed