uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

nixos/doc/manual/administration/maintenance-mode.section.md

@@ -0,0 +1,11 @@
+# Maintenance Mode {#sec-maintenance-mode}
+
+You can enter rescue mode by running:
+
+```ShellSession
+# systemctl rescue
+```
+
+This will eventually give you a single-user root shell. Systemd will
+stop (almost) all system services. To get out of maintenance mode, just
+exit from the rescue shell.