tracing: fix typos in comments

Impact: clean up.

Fix typos in the comments.

Signed-off-by: Wenji Huang <wenji.huang@oracle.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
diff --git a/kernel/trace/trace_hw_branches.c b/kernel/trace/trace_hw_branches.c
index e3e7db6..0794dd3 100644
--- a/kernel/trace/trace_hw_branches.c
+++ b/kernel/trace/trace_hw_branches.c
@@ -75,7 +75,7 @@
 }
 
 /*
- * Start tracing on the current cpu.
+ * Stop tracing on the current cpu.
  * The argument is ignored.
  *
  * pre: bts_tracer_mutex must be locked.