ALSA: usb-audio: Skip volume controls triggers hangup on Dell USB Dock

This is Dell usb dock audio workaround.
It was fixed the master volume keep lower.

[Some background: the patch essentially skips the controls of a couple
of FU volumes. Although the firmware exposes the dB and the value
information via the usb descriptor, changing the values (we set the
min volume as default) screws up the device. Although this has been
fixed in the newer firmware, the devices are shipped with the old
firmware, thus we need the workaround in the driver side. -- tiwai]

Signed-off-by: Kailang Yang <[e-mail]>
Cc: <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

sound/usb/mixer_maps.c

···
 };
 
 /*
+ * Dell usb dock with ALC4020 codec had a firmware problem where it got
+ * screwed up when zero volume is passed; just skip it as a workaround
+ */
+static const struct usbmix_name_map dell_alc4020_map[] = {
+	{ 16, NULL },
+	{ 19, NULL },
+	{ 0 }
+};
+
+/*
  * Control map entries
  */
 
···
 	{
 		.id = USB_ID(0x0ccd, 0x0028),
 		.map = aureon_51_2_map,
+	},
+	{
+		.id = USB_ID(0x0bda, 0x4014),
+		.map = dell_alc4020_map,
 	},
 	{
 		.id = USB_ID(0x0dba, 0x1000),