pinctrl: imx: prepare for making "group_names" in "function_desc" const

The plan for "struct function_desc" is to make its "group_names"
/double/ const. That will allow drivers to use it with static const
data.

This imx change is required to avoid:
drivers/pinctrl/freescale/pinctrl-imx.c: In function 'imx_pinctrl_parse_functions':
drivers/pinctrl/freescale/pinctrl-imx.c:672:24: error: assignment of read-only location '*(func->group_names + (sizetype)(i * 4))'
  672 |   func->group_names[i] = child->name;
      |                        ^
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Link: https://lore.kernel.org/r/20211216162206.8027-1-zajec5@gmail.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/freescale/pinctrl-imx.c

@@ -648,6 +648,7 @@ static int imx_pinctrl_parse_functions(struct device_node *np,
 	struct device_node *child;
 	struct function_desc *func;
 	struct group_desc *grp;
+	const char **group_names;
 	u32 i = 0;
 
 	dev_dbg(pctl->dev, "parse function(%d): %pOFn\n", index, np);
@@ -663,14 +664,16 @@ static int imx_pinctrl_parse_functions(struct device_node *np,
 		dev_err(ipctl->dev, "no groups defined in %pOF\n", np);
 		return -EINVAL;
 	}
-	func->group_names = devm_kcalloc(ipctl->dev, func->num_group_names,
-					 sizeof(char *), GFP_KERNEL);
+
+	group_names = devm_kcalloc(ipctl->dev, func->num_group_names,
+				   sizeof(char *), GFP_KERNEL);
 	if (!func->group_names)
 		return -ENOMEM;
+	for_each_child_of_node(np, child)
+		group_names[i] = child->name;
+	func->group_names = group_names;
 
 	for_each_child_of_node(np, child) {
-		func->group_names[i] = child->name;
-
 		grp = devm_kzalloc(ipctl->dev, sizeof(struct group_desc),
 				   GFP_KERNEL);
 		if (!grp) {