[04.08] use lchan_auto_release to quickly close channel

In some cases, we can try to close the lchan a bit faster than our
lchan release timeout:
* After we've sent LOC UPD ACCEPT and MM INFO
* After a phone has confirmed the RELEASE of a call
1 file changed
tree: 1f2997520dd3a94ed7768bfc76508e8b91dd6518
  1. hlrsync/
  2. linux-kernel/
  3. openbsc/
  4. wireshark/