thermal/drivers/cpufreq_cooling: Fix return of cpufreq_set_cur_state

When setting the cooling device current state from userspace via sysfs,
the operation fails by returning an -EINVAL.

It appears the recent changes with the per-policy frequency QoS
introduced a regression as reported by:

 https://lkml.org/lkml/2020/3/20/599

The function freq_qos_update_request returns 0 or 1 describing update
effectiveness, and a negative error code on failure. However,
cpufreq_set_cur_state returns 0 on success or an error code otherwise.

Consider the QoS update as successful if the function does not return
an error.

Fixes: 3000ce3 ("cpufreq: Use per-policy frequency QoS")
Signed-off-by: Willy Wolff <willy.mh.wolff.ml@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200321092740.7vvwfxsebcrznydh@macmini.local

drivers/thermal/cpufreq_cooling.c

@@ -431,6 +431,7 @@ static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
 				 unsigned long state)
 {
 	struct cpufreq_cooling_device *cpufreq_cdev = cdev->devdata;
+	int ret;
 
 	/* Request state should be less than max_level */
 	if (WARN_ON(state > cpufreq_cdev->max_level))
@@ -442,8 +443,9 @@ static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
 
 	cpufreq_cdev->cpufreq_state = state;
 
-	return freq_qos_update_request(&cpufreq_cdev->qos_req,
-				get_state_freq(cpufreq_cdev, state));
+	ret = freq_qos_update_request(&cpufreq_cdev->qos_req,
+				      get_state_freq(cpufreq_cdev, state));
+	return ret < 0 ? ret : 0;
 }
 
 /* Bind cpufreq callbacks to thermal cooling device ops */