ALSA: ac97: fix device initialization in the compat layer

ac97->dev is an object of 'struct device' type. It should be initialized
via device_initialize() or device_register().

Fixes: 74426fbf ("ALSA: ac97: add an ac97 bus")
Signed-off-by: Lihua Yao <ylhuajnu@163.com>
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/ac97/snd_ac97_compat.c

@@ -15,6 +15,11 @@
 
 #include "ac97_core.h"
 
+static void compat_ac97_release(struct device *dev)
+{
+	kfree(to_ac97_t(dev));
+}
+
 static void compat_ac97_reset(struct snd_ac97 *ac97)
 {
 	struct ac97_codec_device *adev = to_ac97_device(ac97->private_data);
@@ -65,21 +70,31 @@ static struct snd_ac97_bus compat_soc_ac97_bus = {
 struct snd_ac97 *snd_ac97_compat_alloc(struct ac97_codec_device *adev)
 {
 	struct snd_ac97 *ac97;
+	int ret;
 
 	ac97 = kzalloc(sizeof(struct snd_ac97), GFP_KERNEL);
 	if (ac97 == NULL)
 		return ERR_PTR(-ENOMEM);
 
-	ac97->dev = adev->dev;
 	ac97->private_data = adev;
 	ac97->bus = &compat_soc_ac97_bus;
+
+	ac97->dev.parent = &adev->dev;
+	ac97->dev.release = compat_ac97_release;
+	dev_set_name(&ac97->dev, "%s-compat", dev_name(&adev->dev));
+	ret = device_register(&ac97->dev);
+	if (ret) {
+		put_device(&ac97->dev);
+		return ERR_PTR(ret);
+	}
+
 	return ac97;
 }
 EXPORT_SYMBOL_GPL(snd_ac97_compat_alloc);
 
 void snd_ac97_compat_release(struct snd_ac97 *ac97)
 {
-	kfree(ac97);
+	device_unregister(&ac97->dev);
 }
 EXPORT_SYMBOL_GPL(snd_ac97_compat_release);