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>

pkgs/build-support/mono-dll-fixer/default.nix

@@ -0,0 +1,11 @@
+{stdenv, perl}:
+stdenv.mkDerivation {
+  name = "mono-dll-fixer";
+  dllFixer = ./dll-fixer.pl;
+  dontUnpack = true;
+  installPhase = ''
+    substitute $dllFixer $out --subst-var-by perl $perl/bin/perl
+    chmod +x $out
+  '';
+  inherit perl;
+}