ALSA: ppc: Switch to use for_each_child_of_node() macro

Use for_each_child_of_node() macro instead of open coding it.
No functional change.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20220916141108.683080-1-yangyingliang@huawei.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/ppc/tumbler.c

@@ -1060,8 +1060,7 @@ static struct device_node *find_audio_device(const char *name)
 	if (! gpiop)
 		return NULL;
   
-	for (np = of_get_next_child(gpiop, NULL); np;
-			np = of_get_next_child(gpiop, np)) {
+	for_each_child_of_node(gpiop, np) {
 		const char *property = of_get_property(np, "audio-gpio", NULL);
 		if (property && strcmp(property, name) == 0)
 			break;
@@ -1080,8 +1079,7 @@ static struct device_node *find_compatible_audio_device(const char *name)
 	if (!gpiop)
 		return NULL;
   
-	for (np = of_get_next_child(gpiop, NULL); np;
-			np = of_get_next_child(gpiop, np)) {
+	for_each_child_of_node(gpiop, np) {
 		if (of_device_is_compatible(np, name))
 			break;
 	}