l1sap: acch_repetition fix hysthereis threshold table
l1sap: acch_repetition fix hysthereis threshold table

The table in repeated_ul_sacch_active_decision() is derived from the
second table in GSM 05.08 8.2.4 but the first table would be correct.
Also the lower threshold is not properly choosen. A lower threshold,
that derives from upper threshold shifted by 2 makes sense (BER must
improved by 2 RXQUAL steps before repetition is turned off.)

Change-Id: I1d9b5c8abb79938cdecdafed84ed2e5d47e0bd3a
Related: SYS#5114

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