firmware: use power efficient workqueue for unloading and aborting fw load

Allow the scheduler to select the most appropriate CPU for running the
firmware load timeout routine and delayed routine for firmware unload.
This extends idle residency times and conserves power.

This functionality is enabled when CONFIG_WQ_POWER_EFFICIENT is selected.

Cc: Ming Lei <ming.lei@canonical.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Shaibal Dutta <shaibal.dutta@broadcom.com>
[zoran.markovic@linaro.org: Rebased to latest kernel, added commit message.
Fixed code alignment.]
Signed-off-by: Zoran Markovic <zoran.markovic@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/firmware_class.c

@@ -902,7 +902,8 @@ static int _request_firmware_load(struct firmware_priv *fw_priv,
 		dev_set_uevent_suppress(f_dev, false);
 		dev_dbg(f_dev, "firmware: requesting %s\n", buf->fw_id);
 		if (timeout != MAX_SCHEDULE_TIMEOUT)
-			schedule_delayed_work(&fw_priv->timeout_work, timeout);
+			queue_delayed_work(system_power_efficient_wq,
+					   &fw_priv->timeout_work, timeout);
 
 		kobject_uevent(&fw_priv->dev.kobj, KOBJ_ADD);
 	}
@@ -1574,8 +1575,8 @@ static void device_uncache_fw_images_work(struct work_struct *work)
  */
 static void device_uncache_fw_images_delay(unsigned long delay)
 {
-	schedule_delayed_work(&fw_cache.work,
-			msecs_to_jiffies(delay));
+	queue_delayed_work(system_power_efficient_wq, &fw_cache.work,
+			   msecs_to_jiffies(delay));
 }
 
 static int fw_pm_notify(struct notifier_block *notify_block,