ms: restructure the va code to add rach support

This commit adds support for rach bursts to the viterbi equalizer, which is currently only being used by the ms side, so the equalizer can be used by the osmo-trx network side, too. The difference is that rach bursts are shorter than any other burst type (due to unknown TA) and start with diffrent tail bits.

Change-Id: I4a5cedc8c9a3289c75ce7b914eac286e601ebed0
---
M Transceiver52M/grgsm_vitac/constants.h
M Transceiver52M/grgsm_vitac/grgsm_vitac.cpp
M Transceiver52M/grgsm_vitac/grgsm_vitac.h
M Transceiver52M/ms/ms_rx_lower.cpp
M Transceiver52M/ms/ms_upper.cpp
5 files changed, 127 insertions(+), 96 deletions(-)