powercap: idle_inject: Fix warnings with make W=1

Fix following warning at three places:

Function parameter or member 'ii_dev' not described.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/powercap/idle_inject.c

@@ -147,6 +147,7 @@ static void idle_inject_fn(unsigned int cpu)
 
 /**
  * idle_inject_set_duration - idle and run duration update helper
+ * @ii_dev: idle injection control device structure
  * @run_duration_us: CPU run time to allow in microseconds
  * @idle_duration_us: CPU idle time to inject in microseconds
  */
@@ -162,6 +163,7 @@ void idle_inject_set_duration(struct idle_inject_device *ii_dev,
 
 /**
  * idle_inject_get_duration - idle and run duration retrieval helper
+ * @ii_dev: idle injection control device structure
  * @run_duration_us: memory location to store the current CPU run time
  * @idle_duration_us: memory location to store the current CPU idle time
  */
@@ -175,6 +177,7 @@ void idle_inject_get_duration(struct idle_inject_device *ii_dev,
 
 /**
  * idle_inject_set_latency - set the maximum latency allowed
+ * @ii_dev: idle injection control device structure
  * @latency_us: set the latency requirement for the idle state
  */
 void idle_inject_set_latency(struct idle_inject_device *ii_dev,