Changes

osmo_trau_frame_decode_8k: check all sync bits

The decoding of unknown TRAU-8k frames (the direction and 8 kbit/s
submux are wrong, but nothing else) begins by trial-and-error
checking of 4 possible GSM 08.61 sync patterns.  In the case of
classic HR speech/data and AMR-low sync patterns, not all bits
were checked.

Change-Id: I47b055b4d3b92f018508fd7baa0784dfcabe6262