cpufreq: ARM big LITTLE DT: Return correct transition latency

By mistake we are returning zero for successful call to
dt_get_transition_latency(), whereas we should return
transition_latency.  Fix that.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/arm_big_little_dt.c

@@ -78,7 +78,7 @@ static int dt_get_transition_latency(struct device *cpu_dev)
 		of_node_put(np);
 		of_node_put(parent);
 
-		return 0;
+		return transition_latency;
 	}
 
 	return -ENODEV;