tbf: First round of removing llc handling from the rlcmac_data

The code in gprs_rlcmac_data should ask the TBF for help in packing
the frames but it really shouldn't poke in the internals of the
tbf structure. This is very bad capsuling and has plenty of copy
and paste.

At the same thime this will be the most dangerous refactoring of
the code base.
3 files changed