tracing: Missing error code in tracer_alloc_buffers()

If ring_buffer_alloc() or one of the next couple function calls fail
then we should return -ENOMEM but the current code returns success.

Link: http://lkml.kernel.org/r/20170801110201.ajdkct7vwzixahvx@mwanda

Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: stable@vger.kernel.org
Fixes: b32614c0 ('tracing/rb: Convert to hotplug state machine')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -8293,6 +8293,7 @@ __init static int tracer_alloc_buffers(void)
 	if (ret < 0)
 		goto out_free_cpumask;
 	/* Used for event triggers */
+	ret = -ENOMEM;
 	temp_buffer = ring_buffer_alloc(PAGE_SIZE, RB_FL_OVERWRITE);
 	if (!temp_buffer)
 		goto out_rm_hp_state;