thermal: cpu_cooling: update documentation for cpufreq_get_cur_state

Update documentation for cpufreq_get_cur_state callback.
Signed-off-by: Eduardo Valentin <eduardo.valentin@ti.com>
Acked-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

drivers/thermal/cpu_cooling.c

@@ -365,6 +365,11 @@ static int cpufreq_get_max_state(struct thermal_cooling_device *cdev,
  * cpufreq_get_cur_state - callback function to get the current cooling state.
  * @cdev: thermal cooling device pointer.
  * @state: fill this variable with the current cooling state.
+ *
+ * Callback for the thermal cooling device to return the cpufreq
+ * current cooling state.
+ *
+ * Return: 0 on success, an error code otherwise.
  */
 static int cpufreq_get_cur_state(struct thermal_cooling_device *cdev,
 				 unsigned long *state)