Changes

trxcon/fsm: handle_dch_est_req(): do not reset the scheduler

Calling l1sched_reset() results in resetting the UL SACCH cache,
that may have been populated prior to sending L1CTL_DM_EST_REQ.
Instead, do what the comment says - call l1sched_del_all_ts().

Change-Id: Iff03fa5b90ac1ec30b7937cea6bd09c6ececb5f6
Fixes: c6fe9c3f ("trxcon: trxcon_fsm: permit loop [P]DCH transitions")
Related: 15877ba05 ("trxcon: allow populating global SACCH cache via L1CTL")
Related: OS#6919