tracing/hwlat: Don't ignore outer-loop duration when calculating max_latency

max_latency is intended to record the maximum ever observed hardware
latency, which may occur in either part of the loop (inner/outer). So
we need to also consider the outer-loop sample when updating
max_latency.

Link: http://lkml.kernel.org/r/157073345463.17189.18124025522664682811.stgit@srivatsa-ubuntu

Fixes: e7c15cd8 ("tracing: Added hardware latency tracer")
Cc: stable@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_hwlat.c

@@ -256,6 +256,8 @@ static int get_sample(void)
 		/* Keep a running maximum ever recorded hardware latency */
 		if (sample > tr->max_latency)
 			tr->max_latency = sample;
+		if (outer_sample > tr->max_latency)
+			tr->max_latency = outer_sample;
 	}
 
 out: