[PATCH] docs: fix 'make htmldocs' warning in trace

[Anup Sharma <anupnewsmail@xxxxxxxxx>]

Fix following 'make htmldocs' warnings:
Documentation/trace/histogram-design.rst:
WARNING: document isn't included in any toctree

Signed-off-by: Anup Sharma <anupnewsmail@xxxxxxxxx>
---
 Documentation/trace/index.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst
index fa9e1c730f6a..e28c2c2fff7a 100644
--- a/Documentation/trace/index.rst
+++ b/Documentation/trace/index.rst
@@ -19,6 +19,7 @@ Linux Tracing Technologies
    events-msr
    mmiotrace
    histogram
+   histogram-design
    boottime-trace
    hwlat_detector
    intel_th
-- 
2.34.1