Section heading for sched_waking histogram is shown as normal paragraph
instead due to codeblock marker for the following diagram being in the
same line as the section underline. Separate them.

Fixes: daceabf1b494 ("tracing/doc: Fix ascii-art in histogram-design.rst")
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
---
 Documentation/trace/histogram-design.rst | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Documentation/trace/histogram-design.rst b/Documentation/trace/histogram-design.rst
index 231a12bd7d461c..4faff1669b77bd 100644
--- a/Documentation/trace/histogram-design.rst
+++ b/Documentation/trace/histogram-design.rst
@@ -380,7 +380,9 @@ entry, ts0, corresponding to the ts0 variable in the sched_waking
 trigger above.
 
 sched_waking histogram
-----------------------::
+----------------------
+
+.. code-block::
 
   +------------------+
   | hist_data        |<-------------------------------------------------------+
-- 
An old man doll... just what I always wanted! - Clara