osmo-bts-trx/scheduler: also detect TSC for Access Bursts on PDCH
osmo-bts-trx/scheduler: also detect TSC for Access Bursts on PDCH

If a logical channel, on which an Access Burst has been received,
is not either of RACH, PDTCH or PTCCH, then this is a handover
Access Burst, which is always encoded as 8-bit and shall contain
the generic training sequence (TS0).

Access Bursts on a PDCH time-slot are not related to handover.

Change-Id: If7d6135d6c4d7f9bd71d9fab6f8adc3f8cfd10ea

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts