pwm: clk: Make use of devm_pwmchip_alloc() function

This prepares the pwm-clk 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_pwm_clk_chip() helper macro to a static inline to
get some type safety.

Link: https://lore.kernel.org/r/c02ccc955fe7a0aec7ce0ccaf5cd2bd902ae687f.1707900770.git.u.kleine-koenig@pengutronix.deSigned-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

drivers/pwm/pwm-clk.c

@@ -28,12 +28,14 @@
 #include <linux/pwm.h>
 
 struct pwm_clk_chip {
-	struct pwm_chip chip;
 	struct clk *clk;
 	bool clk_enabled;
 };
 
-#define to_pwm_clk_chip(_chip) container_of(_chip, struct pwm_clk_chip, chip)
+static inline struct pwm_clk_chip *to_pwm_clk_chip(struct pwm_chip *chip)
+{
+	return pwmchip_get_drvdata(chip);
+}
 
 static int pwm_clk_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			 const struct pwm_state *state)
@@ -85,19 +87,17 @@ static int pwm_clk_probe(struct platform_device *pdev)
 	struct pwm_clk_chip *pcchip;
 	int ret;
 
-	pcchip = devm_kzalloc(&pdev->dev, sizeof(*pcchip), GFP_KERNEL);
-	if (!pcchip)
-		return -ENOMEM;
-	chip = &pcchip->chip;
+	chip = devm_pwmchip_alloc(&pdev->dev, 1, sizeof(*pcchip));
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+	pcchip = to_pwm_clk_chip(chip);
 
 	pcchip->clk = devm_clk_get_prepared(&pdev->dev, NULL);
 	if (IS_ERR(pcchip->clk))
 		return dev_err_probe(&pdev->dev, PTR_ERR(pcchip->clk),
 				     "Failed to get clock\n");
 
-	chip->dev = &pdev->dev;
 	chip->ops = &pwm_clk_ops;
-	chip->npwm = 1;
 
 	ret = pwmchip_add(chip);
 	if (ret < 0)