ALSA: snd-usb: add snd_usb_audio-wide mutex

This is needed for new card-wide list operations.
Signed-off-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/card.c

@@ -276,6 +276,7 @@ static int snd_usb_create_streams(struct snd_usb_audio *chip, int ctrlif)
 
 static int snd_usb_audio_free(struct snd_usb_audio *chip)
 {
+	mutex_destroy(&chip->mutex);
 	kfree(chip);
 	return 0;
 }
@@ -336,6 +337,7 @@ static int snd_usb_audio_create(struct usb_device *dev, int idx,
 		return -ENOMEM;
 	}
 
+	mutex_init(&chip->mutex);
 	mutex_init(&chip->shutdown_mutex);
 	chip->index = idx;
 	chip->dev = dev;

sound/usb/usbaudio.h

@@ -36,6 +36,7 @@ struct snd_usb_audio {
 	struct snd_card *card;
 	struct usb_interface *pm_intf;
 	u32 usb_id;
+	struct mutex mutex;
 	struct mutex shutdown_mutex;
 	unsigned int shutdown:1;
 	unsigned int probing:1;