move {ts,lchan}2chan_nr() functions to gsm_data_shared.c

... this way osmo-bts can use them
diff --git a/openbsc/include/openbsc/gsm_data_shared.h b/openbsc/include/openbsc/gsm_data_shared.h
index 07ababf..cab5817 100644
--- a/openbsc/include/openbsc/gsm_data_shared.h
+++ b/openbsc/include/openbsc/gsm_data_shared.h
@@ -174,6 +174,8 @@
 	uint8_t rqd_ta;
 
 	struct gsm_subscriber_connection *conn;
+#else
+	struct lapdm_channel lapdm_ch;
 #endif
 };
 
@@ -531,4 +533,7 @@
 gsm_objclass2obj(struct gsm_bts *bts, uint8_t obj_class,
 	     struct abis_om_obj_inst *obj_inst);
 
+uint8_t gsm_ts2chan_nr(const struct gsm_bts_trx_ts *ts, uint8_t lchan_nr);
+uint8_t gsm_lchan2chan_nr(const struct gsm_lchan *lchan);
+
 #endif