pwm: vt8500: 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/c3c45a08f2ccb8bb13b4042c73f93064876586eb.1707900770.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/pwm/pwm-vt8500.c

@@ -63,7 +63,7 @@ static inline void vt8500_pwm_busy_wait(struct pwm_chip *chip, int nr, u8 bitmas
 		cpu_relax();
 
 	if (unlikely(!loops))
-		dev_warn(chip->dev, "Waiting for status bits 0x%x to clear timed out\n",
+		dev_warn(pwmchip_parent(chip), "Waiting for status bits 0x%x to clear timed out\n",
 			 mask);
 }
 
@@ -78,7 +78,7 @@ static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	err = clk_enable(vt8500->clk);
 	if (err < 0) {
-		dev_err(chip->dev, "failed to enable clock\n");
+		dev_err(pwmchip_parent(chip), "failed to enable clock\n");
 		return err;
 	}
 
@@ -129,7 +129,7 @@ static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 
 	err = clk_enable(vt8500->clk);
 	if (err < 0) {
-		dev_err(chip->dev, "failed to enable clock\n");
+		dev_err(pwmchip_parent(chip), "failed to enable clock\n");
 		return err;
 	}