[PATCH] docs: trace/index.rst: add histogram-design.rst

[Daniel W. S. Almeida]

From: Daniel W. S. Almeida <dwlsalme...@gmail.com>

Fix the following warning:

Documentation/trace/histogram-design.rst:
WARNING: document isn't included in any toctree

By adding 'histogram-design.rst' to the index.

Signed-off-by: Daniel W. S. Almeida <dwlsalme...@gmail.com>
---
 Documentation/trace/index.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst
index 7d83156c9ac1f..f44794c8fd840 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
-- 
2.27.0