rsl: Send PDCH ACT NACK if TCH chan is still active
rsl: Send PDCH ACT NACK if TCH chan is still active

Fix recent commit which broke TTCN3 BTS_tests
TC_dyn_ipa_pdch_tchf_act_pdch_act_nack.

Prior to the breaking commit, logic was still not good, because
1- It didn't return after sending the NACK
2- It sent a NACK in all cases, while for PDCH DEACT we want to force
its deactivation. Going through tests it can be seen that indeed it
can deactivate it in that case:
rsl.c:2206 (bts=0,trx=0,ts=3,pchan=TCH/F_PDCH as PDCH) Request to PDCH DEACT, but lchan is still in state ACTIVE
...
rsl.c:2103 (bts=0,trx=0,ts=3,ss=0) Tx PDCH DEACT ACK

Fixes: 133a3d96dc07ebda4dfc7899dab9c0d0c80c9fea ("rsl: Avoid sending ipa PDCH DEACT NACK followed by ACK")
Change-Id: I6d6d12aec10c801fe55012ca6e58d0bc8755b15d

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