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/configuration/package-mgmt.chapter.md

@@ -0,0 +1,18 @@
+# Package Management {#sec-package-management}
+
+This section describes how to add additional packages to your system.
+NixOS has two distinct styles of package management:
+
+-   *Declarative*, where you declare what packages you want in your
+    `configuration.nix`. Every time you run `nixos-rebuild`, NixOS will
+    ensure that you get a consistent set of binaries corresponding to
+    your specification.
+
+-   *Ad hoc*, where you install, upgrade and uninstall packages via the
+    `nix-env` command. This style allows mixing packages from different
+    Nixpkgs versions. It's the only choice for non-root users.
+
+```{=docbook}
+<xi:include href="declarative-packages.section.xml" />
+<xi:include href="ad-hoc-packages.section.xml" />
+```