stat: Explicitly support stat_items without unit
Add OSMO_STAT_ITEM_NO_UNIT for stat items without an unit. The
statsd reporter uses gauges ("g") to report them.
Sponsored-by: On-Waves ehf
diff --git a/include/osmocom/core/stat_item.h b/include/osmocom/core/stat_item.h
index c1466f8..b3a3d9c 100644
--- a/include/osmocom/core/stat_item.h
+++ b/include/osmocom/core/stat_item.h
@@ -13,6 +13,7 @@
struct osmo_stat_item_desc;
#define STAT_ITEM_NOVALUE_ID 0
+#define OSMO_STAT_ITEM_NO_UNIT NULL
struct osmo_stat_item_value {
int32_t id;