thermal: rcar_thermal: Prevent hardware access during system suspend

On r8a7791/koelsch, sometimes the following message is printed during
system suspend:

    rcar_thermal e61f0000.thermal: thermal sensor was broken

This happens if the workqueue runs while the device is already
suspended.  Fix this by using the freezable system workqueue instead,
cfr. commit 51e20d0e ("thermal: Prevent polling from happening
during system suspend").

Fixes: e0a5172e ("thermal: rcar: add interrupt support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/thermal/rcar_thermal.c

@@ -450,8 +450,8 @@ static irqreturn_t rcar_thermal_irq(int irq, void *data)
 	rcar_thermal_for_each_priv(priv, common) {
 		if (rcar_thermal_had_changed(priv, status)) {
 			rcar_thermal_irq_disable(priv);
-			schedule_delayed_work(&priv->work,
-					      msecs_to_jiffies(300));
+			queue_delayed_work(system_freezable_wq, &priv->work,
+					   msecs_to_jiffies(300));
 		}
 	}