nixos/*: automatically convert option descriptions

conversions were done using https://github.com/pennae/nix-doc-munge
using (probably) rev f34e145 running

    nix-doc-munge nixos/**/*.nix
    nix-doc-munge --import nixos/**/*.nix

the tool ensures that only changes that could affect the generated
manual *but don't* are committed, other changes require manual review
and are discarded.

nixos/modules/hardware/corectrl.nix

@@ -7,15 +7,15 @@ let
 in
 {
   options.programs.corectrl = {
-    enable = mkEnableOption ''
+    enable = mkEnableOption (lib.mdDoc ''
       A tool to overclock amd graphics cards and processors.
       Add your user to the corectrl group to run corectrl without needing to enter your password
-    '';
+    '');
 
     gpuOverclock = {
-      enable = mkEnableOption ''
+      enable = mkEnableOption (lib.mdDoc ''
         true
-      '';
+      '');
       ppfeaturemask = mkOption {
         type = types.str;
         default = "0xfffd7fff";