[PATCH -next] tracing: Remove unused extern declaration tracing_map_set_field_descr()

[YueHaibing]

Since commit 08d43a5fa063 ("tracing: Add lock-free tracing_map"),
this is never used, so can be removed.

Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
---
 kernel/trace/tracing_map.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/kernel/trace/tracing_map.h b/kernel/trace/tracing_map.h
index 2c765ee2a4d4..99c37eeebc16 100644
--- a/kernel/trace/tracing_map.h
+++ b/kernel/trace/tracing_map.h
@@ -272,10 +272,6 @@ extern u64 tracing_map_read_sum(struct tracing_map_elt *elt, unsigned int i);
 extern u64 tracing_map_read_var(struct tracing_map_elt *elt, unsigned int i);
 extern u64 tracing_map_read_var_once(struct tracing_map_elt *elt, unsigned int i);
 
-extern void tracing_map_set_field_descr(struct tracing_map *map,
-					unsigned int i,
-					unsigned int key_offset,
-					tracing_map_cmp_fn_t cmp_fn);
 extern int
 tracing_map_sort_entries(struct tracing_map *map,
 			 struct tracing_map_sort_key *sort_keys,
-- 
2.34.1