media: visl: use canonical ftrace path

The canonical location for the tracefs filesystem is at
/sys/kernel/tracing.

But, from Documentation/trace/ftrace.rst:

  Before 4.1, all ftrace tracing control files were within the debugfs
  file system, which is typically located at /sys/kernel/debug/tracing.
  For backward compatibility, when mounting the debugfs file system,
  the tracefs file system will be automatically mounted at:

  /sys/kernel/debug/tracing

Update the visl decoder driver documentation to use this tracefs path.
Signed-off-by: Ross Zwisler <zwisler@google.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Documentation/admin-guide/media/visl.rst

@@ -78,7 +78,7 @@ The trace events are defined on a per-codec basis, e.g.:
 
 .. code-block:: bash
 
-        $ ls /sys/kernel/debug/tracing/events/ | grep visl
+        $ ls /sys/kernel/tracing/events/ | grep visl
         visl_fwht_controls
         visl_h264_controls
         visl_hevc_controls
@@ -90,13 +90,13 @@ For example, in order to dump HEVC SPS data:
 
 .. code-block:: bash
 
-        $ echo 1 >  /sys/kernel/debug/tracing/events/visl_hevc_controls/v4l2_ctrl_hevc_sps/enable
+        $ echo 1 >  /sys/kernel/tracing/events/visl_hevc_controls/v4l2_ctrl_hevc_sps/enable
 
 The SPS data will be dumped to the trace buffer, i.e.:
 
 .. code-block:: bash
 
-        $ cat /sys/kernel/debug/tracing/trace
+        $ cat /sys/kernel/tracing/trace
         video_parameter_set_id 0
         seq_parameter_set_id 0
         pic_width_in_luma_samples 1920