thermal: rcar_thermal: Remove lock in rcar_thermal_get_current_temp()

With the ctemp value returned instead of cached in the private data
structure their is no need to take the lock when translating ctemp into
a temperature.
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200310170029.1648996-4-niklas.soderlund+renesas@ragnatech.se

drivers/thermal/rcar_thermal.c

@@ -254,24 +254,20 @@ static int rcar_thermal_update_temp(struct rcar_thermal_priv *priv)
 static int rcar_thermal_get_current_temp(struct rcar_thermal_priv *priv,
 					 int *temp)
 {
-	int ctemp, tmp;
+	int ctemp;
 
 	ctemp = rcar_thermal_update_temp(priv);
 	if (ctemp < 0)
 		return ctemp;
 
-	mutex_lock(&priv->lock);
+	/* Guaranteed operating range is -45C to 125C. */
+
 	if (priv->chip->ctemp_bands == 1)
-		tmp = MCELSIUS((ctemp * 5) - 65);
+		*temp = MCELSIUS((ctemp * 5) - 65);
 	else if (ctemp < 24)
-		tmp = MCELSIUS(((ctemp * 55) - 720) / 10);
+		*temp = MCELSIUS(((ctemp * 55) - 720) / 10);
 	else
-		tmp = MCELSIUS((ctemp * 5) - 60);
-	mutex_unlock(&priv->lock);
-
-	/* Guaranteed operating range is -45C to 125C. */
-
-	*temp = tmp;
+		*temp = MCELSIUS((ctemp * 5) - 60);
 
 	return 0;
 }