install-device: permit root login with password

Allow password login to the installation this allows doing remote installation
via SSH. All that need to be done on the local machine is:
1. Boot from the installation media
2. Set a password with passwd
3. Enable SSH with systemctl start sshd

It is safe as root doesn't have a password by default
and SSH is disabled by default.

Fixes #20718

nixos/modules/profiles/installation-device.nix

@@ -46,7 +46,12 @@ with lib;
       '';
 
     # Allow sshd to be started manually through "start sshd".
-    services.openssh.enable = true;
+    services.openssh = {
+      enable = true;
+      # Allow password login to the installation, if the user sets a password via "passwd"
+      # It is safe as root doesn't have a password by default and SSH is disabled by default
+      permitRootLogin = "yes";
+    };
     systemd.services.sshd.wantedBy = mkOverride 50 [];
 
     # Enable wpa_supplicant, but don't start it by default.