raspberry-pi/5: don't use overlay

raspberry-pi/5/default.nix

@@ -1,12 +1,13 @@
 { lib, pkgs, config, ... }:
-
+let
+  linux_rpi5 = pkgs.linux_rpi4.override {
+    rpiVersion = 5;
+    argsOverride.defconfig = "bcm2712_defconfig";
+  };
+in
 {
-  nixpkgs.overlays = [
-    (import ./overlay.nix)
-  ];
-
   boot = {
-    kernelPackages = lib.mkDefault (pkgs.linuxPackagesFor pkgs.linux_rpi5);
+    kernelPackages = lib.mkDefault (pkgs.linuxPackagesFor linux_rpi5);
     initrd.availableKernelModules = [
       "nvme"
       "usbhid"

raspberry-pi/5/overlay.nix

@@ -1,6 +0,0 @@
-final: _prev: {
-  linux_rpi5 = final.linux_rpi4.override {
-    rpiVersion = 5;
-    argsOverride.defconfig = "bcm2712_defconfig";
-  };
-}