pwm: dwc: Make use of devm_pwmchip_alloc() function

This prepares the pwm-dwc driver to further changes of the pwm core
outlined in the commit introducing devm_pwmchip_alloc(). There is no
intended semantical change and the driver should behave as before.

Also convert the to_dwc_pwm() helper macro to a static inline to get
some type safety.

Link: https://lore.kernel.org/r/64e64a9a8644600d51b234ad9bcae951b5748998.1707900770.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/pwm/pwm-dwc-core.c

@@ -164,15 +164,13 @@ struct pwm_chip *dwc_pwm_alloc(struct device *dev)
 	struct pwm_chip *chip;
 	struct dwc_pwm *dwc;
 
-	dwc = devm_kzalloc(dev, sizeof(*dwc), GFP_KERNEL);
-	if (!dwc)
-		return ERR_PTR(-ENOMEM);
-	chip = &dwc->chip;
+	chip = devm_pwmchip_alloc(dev, DWC_TIMERS_TOTAL, sizeof(*dwc));
+	if (IS_ERR(chip))
+		return chip;
+	dwc = to_dwc_pwm(chip);
 
 	dwc->clk_ns = 10;
-	chip->dev = dev;
 	chip->ops = &dwc_pwm_ops;
-	chip->npwm = DWC_TIMERS_TOTAL;
 
 	dev_set_drvdata(dev, chip);
 	return chip;

drivers/pwm/pwm-dwc.h

@@ -40,12 +40,15 @@ struct dwc_pwm_ctx {
 };
 
 struct dwc_pwm {
-	struct pwm_chip chip;
 	void __iomem *base;
 	unsigned int clk_ns;
 	struct dwc_pwm_ctx ctx[DWC_TIMERS_TOTAL];
 };
-#define to_dwc_pwm(p)	(container_of((p), struct dwc_pwm, chip))
+
+static inline struct dwc_pwm *to_dwc_pwm(struct pwm_chip *chip)
+{
+	return pwmchip_get_drvdata(chip);
+}
 
 static inline u32 dwc_pwm_readl(struct dwc_pwm *dwc, u32 offset)
 {