f2fs: add spin_lock to cover radix operations in IO tracer

This patch adds spin_lock to cover radix tree operations in IO tracer.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 0ae6a2f..e6f035c 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1222,6 +1222,8 @@
 {
 	int err;
 
+	f2fs_build_trace_ios();
+
 	err = init_inodecache();
 	if (err)
 		goto fail;