refactor(nixos): move hardware config options to machine nixos module

modules/nixos/machine/platform/default.nix

@@ -0,0 +1,21 @@
+{ config, lib, ... }:
+let
+  inherit (lib) singleton mkOption;
+  inherit (lib.types) enum;
+  cfg = config.machine.platform;
+in
+{
+  options.machine.platform = {
+    type = mkOption {
+      type = enum [
+        "amd"
+        "intel"
+      ];
+    };
+  };
+
+  config = {
+    hardware.cpu.${cfg.type}.updateMicrocode = true;
+    boot.kernelModules = singleton "kvm-${cfg.type}";
+  };
+}