ALSA: snd-usb-6fire: add individual volume control for analog channels

Add a stereo volume control for every analog output pair 1/2, 3/4, 5/6.

Signed-off-by: Torsten Schenk <torsten.schenk@zoho.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/6fire/control.h b/sound/usb/6fire/control.h
index 0dcb1d2..ce02411 100644
--- a/sound/usb/6fire/control.h
+++ b/sound/usb/6fire/control.h
@@ -43,7 +43,8 @@
 	bool line_phono_switch;
 	bool digital_thru_switch;
 	bool usb_streaming;
-	u8 master_vol;
+	u8 output_vol[6];
+	u8 ovol_updated;
 };
 
 int __devinit usb6fire_control_init(struct sfire_chip *chip);