UPSTREAM: 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 <kailang@realtek.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

BUG=chrome-os-partner:48451
TEST=Manual test Dell usb dock

Change-Id: I90764e3e41223232c395cd6780d3aea5c60e3059
Reviewed-on: https://chromium-review.googlesource.com/345351
Commit-Ready: Hsinyu Chao <hychao@chromium.org>
Tested-by: Hsinyu Chao <hychao@chromium.org>
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
diff --git a/sound/usb/mixer_maps.c b/sound/usb/mixer_maps.c
index 6a803ef..acf2e88 100644
--- a/sound/usb/mixer_maps.c
+++ b/sound/usb/mixer_maps.c
@@ -356,6 +356,16 @@
 };
 
 /*
+ * 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
  */
 
@@ -438,6 +448,10 @@
 		.map = aureon_51_2_map,
 	},
 	{
+		.id = USB_ID(0x0bda, 0x4014),
+		.map = dell_alc4020_map,
+	},
+	{
 		.id = USB_ID(0x0dba, 0x1000),
 		.map = mbox1_map,
 	},