kefka: Remove the Headphone MixerName from the kernelnext audio config.

When cras mutes an audio output, it switches off the corresponding
switch. On kefka running 4.19, turning off the headphone switch stops
the codec from consuming audio samples, causing playback to block.

Remove the MixerName from the Headphone device for kefka-kernelnext so
cras won't disable the Headphone Switch when muting. Set the Headphone
Output Volume to the maximum value when enabling the Headphone device
to retain use of the full volume range.

BUG=b:138176293
TEST=Video playback continues when muting headphones and headphone
     volume levels are consistent with before this change

Change-Id: I98f67e596ee22bcc2be3792acec51f6550da2af7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/board-overlays/+/1928535
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Sam McNally <sammc@chromium.org>
Commit-Queue: Sam McNally <sammc@chromium.org>
(cherry picked from commit 15fd31198ed5d9519c7d66852c91c3f18980707f)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/board-overlays/+/1962026
Reviewed-by: Sam McNally <sammc@chromium.org>
diff --git a/overlay-kefka/chromeos-base/chromeos-bsp-kefka/chromeos-bsp-kefka-0.0.1-r21.ebuild b/overlay-kefka/chromeos-base/chromeos-bsp-kefka/chromeos-bsp-kefka-0.0.1-r21.ebuild
new file mode 120000
index 0000000..2e4f006
--- /dev/null
+++ b/overlay-kefka/chromeos-base/chromeos-bsp-kefka/chromeos-bsp-kefka-0.0.1-r21.ebuild
@@ -0,0 +1 @@
+chromeos-bsp-kefka-0.0.1.ebuild
\ No newline at end of file
diff --git a/overlay-kefka/chromeos-base/chromeos-bsp-kefka/files/kernelnext-audio-config/ucm-config/chtrt5650/HiFi.conf b/overlay-kefka/chromeos-base/chromeos-bsp-kefka/files/kernelnext-audio-config/ucm-config/chtrt5650/HiFi.conf
index 15a388a..696b742 100644
--- a/overlay-kefka/chromeos-base/chromeos-bsp-kefka/files/kernelnext-audio-config/ucm-config/chtrt5650/HiFi.conf
+++ b/overlay-kefka/chromeos-base/chromeos-bsp-kefka/files/kernelnext-audio-config/ucm-config/chtrt5650/HiFi.conf
@@ -125,7 +125,6 @@
 SectionDevice."Headphone".0 {
 	Value {
 		PlaybackPCM "hw:chtrt5650,0"
-		MixerName "Headphone"
 		JackName "chtrt5650 Headset"
 		JackType "gpio"
 	}
@@ -135,6 +134,7 @@
 
 		cset "name='Ext Spk Switch' off"
 		cset "name='Headphone Switch' on"
+		cset "name='Headphone Playback Volume' 39 39"
 	]
 	DisableSequence [
 		cdev "hw:chtrt5650"