LCLS: add GCR comparison helper

Change-Id: I9e3b5560a058b976638d03cb819415d237ae9984
diff --git a/src/gsm/libosmogsm.map b/src/gsm/libosmogsm.map
index 60ce5d1..f9e9b8b 100644
--- a/src/gsm/libosmogsm.map
+++ b/src/gsm/libosmogsm.map
@@ -240,6 +240,7 @@
 
 osmo_enc_gcr;
 osmo_dec_gcr;
+osmo_gcr_eq;
 
 gsm0858_rsl_ul_meas_enc;