tracing/core: fix missing mutex unlock on tracing_set_tracer()

Impact: fix possible locking imbalance

In case of ring buffer resize failure, tracing_set_tracer forgot to
release trace_types_lock. Fix it.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237151439-6755-5-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace.c

@@ -2494,7 +2494,7 @@ static int tracing_set_tracer(const char *buf)
 	if (!ring_buffer_expanded) {
 		ret = tracing_resize_ring_buffer(trace_buf_size);
 		if (ret < 0)
-			return ret;
+			goto out;
 		ret = 0;
 	}