skipper: move boot related config

hosts/skipper/boot/default.nix

@@ -1,11 +1,14 @@
-{ lib
-, pkgs
-, ...
-}: {
-  environment.etc."secureboot" = {
+{ lib, pkgs, ... }: {
+  imports = [ ./plymouth.nix ];
+  environment = {
+    etc."secureboot" = {
       mode = "symlink";
       source = "/persist/secrets/secureboot";
     };
+    systemPackages = with pkgs; [
+      sbctl
+    ];
+  };
   boot = {
     bootspec.enable = true;
     loader = {
@@ -17,7 +20,4 @@
       pkiBundle = "/persist/secrets/secureboot";
     };
   };
-  environment.systemPackages = with pkgs; [
-    sbctl
-  ];
 }

hosts/skipper/default.nix

@@ -1,13 +1,12 @@
 { pkgs, ... }: {
   imports = [
+    ./boot
     ./hardware
     ./programs
     ./services
     ./network
     ./persistence
     ./virtualisation
-    ./plymouth.nix
-    ./secureboot.nix
     ./security.nix
   ];