nixos: add support for dm-verity

Co-authored-by: nikstur <nikstur@outlook.com>
Co-authored-by: WilliButz <willibutz@posteo.de>

nixos/modules/module-list.nix

@@ -1625,6 +1625,7 @@
   ./system/boot/stage-2.nix
   ./system/boot/systemd.nix
   ./system/boot/systemd/coredump.nix
+  ./system/boot/systemd/dm-verity.nix
   ./system/boot/systemd/initrd-secrets.nix
   ./system/boot/systemd/initrd.nix
   ./system/boot/systemd/journald.nix