lchan release in error state: SACCH deact only for SACCH pchans

This is useful particularly in case where we deactivate PDCHs
which don't have a SACCH associated.  The existin code would
always attempt to deactivate a SACCH even in those cases, leading
to the BTS responsding with related error messages.

Change-Id: Iaf46782329b38ba8f3d438e6c75c2d467b852734
diff --git a/openbsc/src/libcommon/gsm_data_shared.c b/openbsc/src/libcommon/gsm_data_shared.c
index df204fe..387af70 100644
--- a/openbsc/src/libcommon/gsm_data_shared.c
+++ b/openbsc/src/libcommon/gsm_data_shared.c
@@ -729,7 +729,7 @@
 };
 
 /*! Return the actual pchan type, also heeding dynamic TS. */
-static enum gsm_phys_chan_config ts_pchan(struct gsm_bts_trx_ts *ts)
+enum gsm_phys_chan_config ts_pchan(struct gsm_bts_trx_ts *ts)
 {
 	switch (ts->pchan) {
 	case GSM_PCHAN_TCH_F_TCH_H_PDCH: