formats/sd-aarch64: use nixpkgs import

formats/sd-aarch64.nix

@@ -1,54 +1,8 @@
 { config, lib, pkgs, modulesPath, ... }:
-let
-  extlinux-conf-builder =
-    import "${toString modulesPath}/system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.nix" {
-      pkgs = pkgs.buildPackages;
-    };
-
-in {
+{
   imports = [
-    "${toString modulesPath}/installer/sd-card/sd-image.nix"
+    "${toString modulesPath}/installer/sd-card/sd-image-aarch64.nix"
   ];
 
-  boot.loader = {
-    grub.enable = false;
-    generic-extlinux-compatible.enable = true;
-  };
-
-  boot.consoleLogLevel = lib.mkDefault 7;
-
-  # The serial ports listed here are:
-  # - ttyS0: for Tegra (Jetson TX1)
-  # - ttyAMA0: for QEMU's -machine virt
-  # Also increase the amount of CMA to ensure the virtual console on the RPi3 works.
-  boot.kernelParams = ["cma=32M" "console=ttyS0,115200n8" "console=ttyAMA0,115200n8" "console=tty0"];
-
-  sdImage = {
-    populateFirmwareCommands = let
-      configTxt = pkgs.writeText "config.txt" ''
-        kernel=u-boot-rpi3.bin
-
-        # Boot in 64-bit mode.
-        arm_control=0x200
-
-        # U-Boot used to need this to work, regardless of whether UART is actually used or not.
-        # TODO: check when/if this can be removed.
-        enable_uart=1
-
-        # 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
-      '';
-      in ''
-        (cd ${pkgs.raspberrypifw}/share/raspberrypi/boot && cp bootcode.bin fixup*.dat start*.elf $NIX_BUILD_TOP/firmware/)
-        cp ${pkgs.ubootRaspberryPi3_64bit}/u-boot.bin firmware/u-boot-rpi3.bin
-        cp ${configTxt} firmware/config.txt
-      '';
-    populateRootCommands = ''
-      mkdir -p ./files/boot
-      ${extlinux-conf-builder} -t 3 -c ${config.system.build.toplevel} -d ./files/boot
-    '';
-  };
-
   formatAttr = "sdImage";
 }