osmocore: Add utility function rsl_chan_nr_str to RSL

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/include/osmocore/rsl.h b/include/osmocore/rsl.h
index cd84057..54d6703 100644
--- a/include/osmocore/rsl.h
+++ b/include/osmocore/rsl.h
@@ -17,6 +17,9 @@
 uint8_t rsl_enc_chan_nr(uint8_t type, uint8_t subch, uint8_t timeslot);
 /* decode channel number as per Section 9.3.1 */
 int rsl_dec_chan_nr(uint8_t chan_nr, uint8_t *type, uint8_t *subch, uint8_t *timeslot);
+/* Turns channel number into a string */
+const char *rsl_chan_nr_str(uint8_t chan_nr);
+
 
 const char *rsl_err_name(uint8_t err);
 const char *rsl_rlm_cause_name(uint8_t err);