pwm: iqs620a: Prepare removing pwm_chip from driver data

This prepares the driver for further changes that will drop struct
pwm_chip chip from struct iqs620_pwm_private. The only two functions
that make use of struct iqs620_pwm_private::chip (apart from the probe
function that is handled later when converting to pwmchip_alloc()) only
use the chip's device pointer. Introduce such a pointer in driver data
and use that instead.

Link: https://lore.kernel.org/r/e6b1636c0d26d8bcb02a66b2963e2cc394014d76.1707900770.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/pwm/pwm-iqs620a.c

@@ -34,6 +34,7 @@
 
 struct iqs620_pwm_private {
 	struct iqs62x_core *iqs62x;
+	struct device *dev;
 	struct pwm_chip chip;
 	struct notifier_block notifier;
 	struct mutex lock;
@@ -160,7 +161,7 @@ static int iqs620_pwm_notifier(struct notifier_block *notifier,
 	mutex_unlock(&iqs620_pwm->lock);
 
 	if (ret) {
-		dev_err(iqs620_pwm->chip.dev,
+		dev_err(iqs620_pwm->dev,
 			"Failed to re-initialize device: %d\n", ret);
 		return NOTIFY_BAD;
 	}
@@ -181,7 +182,7 @@ static void iqs620_pwm_notifier_unregister(void *context)
 	ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
 						 &iqs620_pwm->notifier);
 	if (ret)
-		dev_err(iqs620_pwm->chip.dev,
+		dev_err(iqs620_pwm->dev,
 			"Failed to unregister notifier: %d\n", ret);
 }
 
@@ -196,6 +197,7 @@ static int iqs620_pwm_probe(struct platform_device *pdev)
 	if (!iqs620_pwm)
 		return -ENOMEM;
 
+	iqs620_pwm->dev = &pdev->dev;
 	iqs620_pwm->iqs62x = iqs62x;
 
 	ret = regmap_read(iqs62x->regmap, IQS620_PWR_SETTINGS, &val);