ALSA: snd_usb_audio: ignore ctrl errors on QuickCam Pro for Notebooks

This webcam works mostly ok, exept with skype.
Skype sends lots of ctrl messages to dynamically ajust
record level. If for some reasons it pokes some error
every thing goes broken:
- first pulseaudio blocks sound for all apps
- then video is reseted
- then skype freez

dmesg has lots of messages like:
cannot set freq 16000 to ep 0x86"

Setting ignore_ctl_error=1 fixes this problem.
Signed-off-by: Oleksij Rempel <bug-track@fisher-privat.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/mixer_maps.c

@@ -341,6 +341,10 @@ static struct usbmix_ctl_map usbmix_ctl_maps[] = {
 		.map = audigy2nx_map,
 		.selector_map = audigy2nx_selectors,
 	},
+	{	/* Logitech, Inc. QuickCam Pro for Notebooks */
+		.id = USB_ID(0x046d, 0x0991),
+		.ignore_ctl_error = 1,
+	},
 	{	/* Logitech, Inc. QuickCam E 3500 */
 		.id = USB_ID(0x046d, 0x09a4),
 		.ignore_ctl_error = 1,