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/installer/sd-card/sd-image-raspberrypi.nix

@@ -0,0 +1,41 @@
+# To build, use:
+# nix-build nixos -I nixos-config=nixos/modules/installer/sd-card/sd-image-raspberrypi.nix -A config.system.build.sdImage
+{ config, lib, pkgs, ... }:
+
+{
+  imports = [
+    ../../profiles/base.nix
+    ./sd-image.nix
+  ];
+
+  boot.loader.grub.enable = false;
+  boot.loader.generic-extlinux-compatible.enable = true;
+
+  boot.consoleLogLevel = lib.mkDefault 7;
+  boot.kernelPackages = pkgs.linuxKernel.packages.linux_rpi1;
+
+  sdImage = {
+    populateFirmwareCommands = let
+      configTxt = pkgs.writeText "config.txt" ''
+        # Prevent the firmware from smashing the framebuffer setup done by the mainline kernel
+        # when attempting to show low-voltage or overtemperature warnings.
+        avoid_warnings=1
+
+        [pi0]
+        kernel=u-boot-rpi0.bin
+
+        [pi1]
+        kernel=u-boot-rpi1.bin
+      '';
+      in ''
+        (cd ${pkgs.raspberrypifw}/share/raspberrypi/boot && cp bootcode.bin fixup*.dat start*.elf $NIX_BUILD_TOP/firmware/)
+        cp ${pkgs.ubootRaspberryPiZero}/u-boot.bin firmware/u-boot-rpi0.bin
+        cp ${pkgs.ubootRaspberryPi}/u-boot.bin firmware/u-boot-rpi1.bin
+        cp ${configTxt} firmware/config.txt
+      '';
+    populateRootCommands = ''
+      mkdir -p ./files/boot
+      ${config.boot.loader.generic-extlinux-compatible.populateCmd} -c ${config.system.build.toplevel} -d ./files/boot
+    '';
+  };
+}