pwm: rcar: Make use of pwmchip_parent() accessor

struct pwm_chip::dev is about to change. To not have to touch this
driver in the same commit as struct pwm_chip::dev, use the accessor
function provided for exactly this purpose.

Link: https://lore.kernel.org/r/8b33a106c84517430d90ee4a8dcb878d0fc3bad5.1707900770.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/pwm/pwm-rcar.c

@@ -132,12 +132,12 @@ static int rcar_pwm_set_counter(struct rcar_pwm_chip *rp, int div, int duty_ns,
 
 static int rcar_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
 {
-	return pm_runtime_get_sync(chip->dev);
+	return pm_runtime_get_sync(pwmchip_parent(chip));
 }
 
 static void rcar_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
 {
-	pm_runtime_put(chip->dev);
+	pm_runtime_put(pwmchip_parent(chip));
 }
 
 static int rcar_pwm_enable(struct rcar_pwm_chip *rp)