dell/xps/9360: drop qca6174 firmware

This was used because the firmware in linux-firmware was outdated.
It should not be after a year.

dell/xps/13-9360/default.nix

@@ -18,13 +18,6 @@
     systemd-boot.enable = lib.mkDefault true;
   };
 
-  hardware.firmware = lib.mkBefore [ pkgs.qca6174-firmware ];
-
-  # TODO: upstream to NixOS/nixpkgs
-  nixpkgs.overlays = [(final: previous: {
-    qca6174-firmware = final.callPackage ./qca6174-firmware.nix {};
-  })];
-
   # This will save you money and possibly your life!
   services.thermald.enable = true;
 }

dell/xps/13-9360/qca6174-firmware.nix

@@ -1,26 +0,0 @@
-{ stdenv, fetchurl }:
-
-stdenv.mkDerivation rec {
-  name = "${target}-firmware-${version}";
-  version = "${branch}-00042";
-
-  branch = "4.4.1.c1";
-  target = "QCA6174";
-
-  src = fetchurl {
-    url = "https://github.com/kvalo/ath10k-firmware/raw/952afa4949cb34193040cd4e7441e1aee50ac731/${target}/hw3.0/${branch}/firmware-6.bin_RM.${version}-QCARMSWP-1";
-    sha256 = "01vvz3qhqw5l3yilcqgk1spk4y9k4qy7na7a57cbl037r231szdh";
-  };
-
-  buildCommand = ''
-    install -D $src $out/lib/firmware/ath10k/${target}/hw3.0/firmware-6.bin
-  '';
-
-  meta = with stdenv.lib; {
-    description = "Updated firmware for the qca6174 wireless chip";
-    homepage = "https://github.com/kvalo/ath10k-firmware/tree/master/QCA6174/hw3.0";
-    license = licenses.unfreeRedistributable;
-    maintainers = with maintainers; [ yorickvp ];
-    platforms = platforms.linux;
-  };
-}