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/modules/misc/passthru.nix

@@ -0,0 +1,16 @@
+# This module allows you to export something from configuration
+# Use case: export kernel source expression for ease of configuring
+
+{ lib, ... }:
+
+{
+  options = {
+    passthru = lib.mkOption {
+      visible = false;
+      description = ''
+        This attribute set will be exported as a system attribute.
+        You can put whatever you want here.
+      '';
+    };
+  };
+}