ALSA: usb-audio: Adjust Gamecom 780 volume level

Original patch fixed the original problem, but the sound was far too low
for most users. This patch references a compare matrix to allow the
volume levels to act normally. I personally tested this patch myself,
and volume levels returned to normal. Please see this discussion for
more details: https://bugzilla.kernel.org/show_bug.cgi?id=65251

Signed-off-by: Paul S McSpadden <fisch602@gmail.com>
Cc: <stable@vger.kernel.org> [v3.14+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/quirks.c

@@ -670,7 +670,7 @@ static int snd_usb_gamecon780_boot_quirk(struct usb_device *dev)
 	/* set the initial volume and don't change; other values are either
 	 * too loud or silent due to firmware bug (bko#65251)
 	 */
-	u8 buf[2] = { 0x74, 0xdc };
+	u8 buf[2] = { 0x74, 0xe3 };
 	return snd_usb_ctl_msg(dev, usb_sndctrlpipe(dev, 0), UAC_SET_CUR,
 			USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
 			UAC_FU_VOLUME << 8, 9 << 8, buf, 2);