rate_ctr: Add functions to reset rate counter (groups)

Change-Id: If2f806d044cd0fb6929dac44ef8f8a15941ffe9b
Related: SYS#4877
diff --git a/include/osmocom/core/rate_ctr.h b/include/osmocom/core/rate_ctr.h
index f7e6e22..1669ce4 100644
--- a/include/osmocom/core/rate_ctr.h
+++ b/include/osmocom/core/rate_ctr.h
@@ -116,4 +116,7 @@
 
 int rate_ctr_for_each_group(rate_ctr_group_handler_t handle_group, void *data);
 
+void rate_ctr_reset(struct rate_ctr *ctr);
+void rate_ctr_group_reset(struct rate_ctr_group *ctrg);
+
 /*! @} */