Disable onboard audio on pi

hosts/pi/default.nix

@@ -19,6 +19,25 @@
       enable = true;
       filter = "*rpi-4-*.dtb";
       overlays = [
+        {
+          name = "audio-off-overlay";
+          dtsText = ''
+            /dts-v1/;
+            /plugin/;
+
+            / {
+              compatible = "brcm,bcm2711";
+
+              fragment@0 {
+                target = <&vchiq>;
+
+                __overlay__ {
+                  status = "disabled";
+                };
+              };
+            };
+          '';
+        }
         {
           # Adapted from: https://github.com/raspberrypi/linux/blob/rpi-6.1.y/arch/arm/boot/dts/overlays/hifiberry-digi-pro-overlay.dts
           # changes: