homestar: Add side-volume-button switch up/down

In tablet mode,the volume buttons should switch function when rotating the tablet.

BUG=b:194362453

TEST=Rotate screen volume down/up function switch

Change-Id: I763b4bf90d7278489bd0d2d41288f70f0574c3da
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/board-overlays/+/3048450
Reviewed-by: Bob Moragues <moragues@chromium.org>
Reviewed-by: Philip Chen <philipchen@chromium.org>
Tested-by: cong yang <yangcong5@huaqin.corp-partner.google.com>
Commit-Queue: Douglas Anderson <dianders@chromium.org>
(cherry picked from commit 8d36a5d1f23c1426b26f345a22425c5aa315bb2c)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/board-overlays/+/3070805
Commit-Queue: Bob Moragues <moragues@chromium.org>
diff --git a/overlay-strongbad/chromeos-base/chromeos-config-bsp-strongbad/files/model.yaml b/overlay-strongbad/chromeos-base/chromeos-config-bsp-strongbad/files/model.yaml
index 778a077..078be78 100644
--- a/overlay-strongbad/chromeos-base/chromeos-config-bsp-strongbad/files/model.yaml
+++ b/overlay-strongbad/chromeos-base/chromeos-config-bsp-strongbad/files/model.yaml
@@ -81,6 +81,15 @@
   ui:
     handwriting-recognition-web-platform-api: true
 
+homestar-button-settings: &homestar_button_settings
+  ui:
+    power-button:
+      edge: left
+      position: "0.88"
+    side-volume-button:
+      region: screen
+      side: top
+
 chromeos:
   devices:
     - $device-name: "coachz"
@@ -101,5 +110,6 @@
       $card: "sc7180-rt5682-max98357a-1mic"
       skus:
         - $sku-id: 0
-          config: *detachable_config
+          config:
+            <<: [ *detachable_config, *homestar_button_settings ]