counters: add osmo_counters_count() returns the amount of counters

Change-Id: I9068231d71876e06d27ee67a688d7fb611ac3a1b
diff --git a/src/counter.c b/src/counter.c
index 0fa84c8..0fa3166 100644
--- a/src/counter.c
+++ b/src/counter.c
@@ -77,6 +77,13 @@
 	return rc;
 }
 
+/*! Counts the registered counter
+ *  \returns amount of counters */
+int osmo_counters_count()
+{
+	return llist_count(&counters);
+}
+
 /*! Find a counter by its name.
  *  \param[in] name Name used to look-up/search counter
  *  \returns Counter on success; NULL if not found */