Move all of NixOS to nixos/ in preparation of the repository merge

nixos/modules/hardware/cpu/amd-microcode.nix

@@ -0,0 +1,29 @@
+{ config, pkgs, ... }:
+
+with pkgs.lib;
+
+{
+
+  ###### interface
+
+  options = {
+
+    hardware.cpu.amd.updateMicrocode = mkOption {
+      default = false;
+      type = types.bool;
+      description = ''
+        Update the CPU microcode for AMD processors.
+      '';
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = mkIf config.hardware.cpu.amd.updateMicrocode {
+    hardware.firmware = [ "${pkgs.amdUcode}/lib/firmware" ];
+    boot.kernelModules = [ "microcode" ];
+  };
+
+}