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/os-specific/linux/device-tree/default.nix

@@ -0,0 +1,32 @@
+{ lib, stdenvNoCC, dtc }:
+
+with lib; {
+  applyOverlays = (base: overlays': stdenvNoCC.mkDerivation {
+    name = "device-tree-overlays";
+    nativeBuildInputs = [ dtc ];
+    buildCommand = let
+      overlays = toList overlays';
+    in ''
+      mkdir -p $out
+      cd ${base}
+      find . -type f -name '*.dtb' -print0 \
+        | xargs -0 cp -v --no-preserve=mode --target-directory $out --parents
+
+      for dtb in $(find $out -type f -name '*.dtb'); do
+        dtbCompat="$( fdtget -t s $dtb / compatible )"
+
+        ${flip (concatMapStringsSep "\n") overlays (o: ''
+        overlayCompat="$( fdtget -t s ${o.dtboFile} / compatible )"
+        # overlayCompat in dtbCompat
+        if [[ "$dtbCompat" =~ "$overlayCompat" ]]; then
+          echo "Applying overlay ${o.name} to $( basename $dtb )"
+          mv $dtb{,.in}
+          fdtoverlay -o "$dtb" -i "$dtb.in" ${o.dtboFile};
+          rm $dtb.in
+        fi
+        '')}
+
+      done
+    '';
+  });
+}