pwm: sifive: 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/170c3c61707992cbc57dce31f70c168fcd3dbe51.1707900770.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/pwm/pwm-sifive.c

@@ -186,7 +186,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (!enabled) {
 		ret = clk_enable(ddata->clk);
 		if (ret) {
-			dev_err(chip->dev, "Enable clk failed\n");
+			dev_err(pwmchip_parent(chip), "Enable clk failed\n");
 			return ret;
 		}
 	}