pwm: ep93xx: 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/3bf56f20bc7f749e5a353cdcfad11dd1ba573381.1707900770.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/pwm/pwm-ep93xx.c

@@ -46,14 +46,14 @@ static inline struct ep93xx_pwm *to_ep93xx_pwm(struct pwm_chip *chip)
 
 static int ep93xx_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
 {
-	struct platform_device *pdev = to_platform_device(chip->dev);
+	struct platform_device *pdev = to_platform_device(pwmchip_parent(chip));
 
 	return ep93xx_pwm_acquire_gpio(pdev);
 }
 
 static void ep93xx_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
 {
-	struct platform_device *pdev = to_platform_device(chip->dev);
+	struct platform_device *pdev = to_platform_device(pwmchip_parent(chip));
 
 	ep93xx_pwm_release_gpio(pdev);
 }