pwm: sun4i: 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.
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/3ddaec73f3abefb45625d0a469026fa8d13da8c0.1707900770.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/pwm/pwm-sun4i.c

@@ -245,7 +245,7 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (!cstate.enabled) {
 		ret = clk_prepare_enable(sun4i_pwm->clk);
 		if (ret) {
-			dev_err(chip->dev, "failed to enable PWM clock\n");
+			dev_err(pwmchip_parent(chip), "failed to enable PWM clock\n");
 			return ret;
 		}
 	}
@@ -253,7 +253,7 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	ret = sun4i_pwm_calculate(sun4i_pwm, state, &duty, &period, &prescaler,
 				  &bypass);
 	if (ret) {
-		dev_err(chip->dev, "period exceeds the maximum value\n");
+		dev_err(pwmchip_parent(chip), "period exceeds the maximum value\n");
 		if (!cstate.enabled)
 			clk_disable_unprepare(sun4i_pwm->clk);
 		return ret;