tbf: Remove the TLLI from the TBFs

Currently the TLLI is stored in each TBF. Since each MS is now
represented by a GprsMs object which takes care of TLLI updating,
and each TBF that has been associated with an TLLI also contains a
reference to a GprsMs object, per TBF TLLI handling is no longer
needed. Keeping all TBF m_tlli members up to date is complex and
doesn't currently work correctly in all circumstances.

This commit removes m_tlli and related members from the TBF class and
the tbf_by_tlli functions from the BTS class.

Ticket: #1674
Sponsored-by: On-Waves ehf
8 files changed