ALSA: usb-audio - Add ignore_ctl_error parameter

Added the ignore_ctl_error parameter to enable/disable the control-error
handling for mixer interfaces.  It was a hard-coded ifdef, and now you
can change it more easily.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
diff --git a/sound/usb/usbaudio.h b/sound/usb/usbaudio.h
index 140ba36..f3ca77f 100644
--- a/sound/usb/usbaudio.h
+++ b/sound/usb/usbaudio.h
@@ -223,7 +223,8 @@
 		    __u8 request, __u8 requesttype, __u16 value, __u16 index,
 		    void *data, __u16 size, int timeout);
 
-int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif);
+int snd_usb_create_mixer(struct snd_usb_audio *chip, int ctrlif,
+			 int ignore_error);
 void snd_usb_mixer_disconnect(struct list_head *p);
 
 int snd_usb_create_midi_interface(struct snd_usb_audio *chip, struct usb_interface *iface,