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/development/importing-modules.section.md

@@ -0,0 +1,46 @@
+# Importing Modules {#sec-importing-modules}
+
+Sometimes NixOS modules need to be used in configuration but exist
+outside of Nixpkgs. These modules can be imported:
+
+```nix
+{ config, lib, pkgs, ... }:
+
+{
+  imports =
+    [ # Use a locally-available module definition in
+      # ./example-module/default.nix
+        ./example-module
+    ];
+
+  services.exampleModule.enable = true;
+}
+```
+
+The environment variable `NIXOS_EXTRA_MODULE_PATH` is an absolute path
+to a NixOS module that is included alongside the Nixpkgs NixOS modules.
+Like any NixOS module, this module can import additional modules:
+
+```nix
+# ./module-list/default.nix
+[
+  ./example-module1
+  ./example-module2
+]
+```
+
+```nix
+# ./extra-module/default.nix
+{ imports = import ./module-list.nix; }
+```
+
+```nix
+# NIXOS_EXTRA_MODULE_PATH=/absolute/path/to/extra-module
+{ config, lib, pkgs, ... }:
+
+{
+  # No `imports` needed
+
+  services.exampleModule1.enable = true;
+}
+```