pinctrl: stm32: Replace custom code by gpiochip_node_count() call

Since we have generic function to count GPIO controller nodes
under a given device, there is no need to open code it. Replace
custom code by gpiochip_node_count() call.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Fabien Dessenne <fabien.dessenne@foss.st.com>

drivers/pinctrl/stm32/pinctrl-stm32.c

@@ -1423,7 +1423,8 @@ int stm32_pctl_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct stm32_pinctrl *pctl;
 	struct pinctrl_pin_desc *pins;
-	int i, ret, hwlock_id, banks = 0;
+	int i, ret, hwlock_id;
+	unsigned int banks;
 
 	if (!np)
 		return -EINVAL;
@@ -1513,10 +1514,7 @@ int stm32_pctl_probe(struct platform_device *pdev)
 		return PTR_ERR(pctl->pctl_dev);
 	}
 
-	for_each_available_child_of_node(np, child)
-		if (of_property_read_bool(child, "gpio-controller"))
-			banks++;
-
+	banks = gpiochip_node_count(dev);
 	if (!banks) {
 		dev_err(dev, "at least one GPIO bank is required\n");
 		return -EINVAL;