linuxPackages.rtl8821au: mark broken on kernel versions < 5.4 and > 6.14

- On Hydra, builds for kernel version  5_10, 5_15, 6_1, 6_6 and 6_12
  succeed, but the build for the latest latest kernel version 6_17 is
  failing.

- The upstream provider of the driver only supports kernel versions
  between version 5.4 and 6.14, inclusive. This is partly because a
  driver has been up-streamed into the kernel, so the package is not
  needed for recent drivers.

  [Reference](https://github.com/morrownr/8821au-20210708.)

- Because of this, mark the driver as broken on the relevant kernel
  versions.

pkgs/os-specific/linux/rtl8821au/default.nix

@@ -66,5 +66,6 @@ stdenv.mkDerivation {
     license = licenses.gpl2Only;
     platforms = lib.platforms.linux;
     maintainers = with maintainers; [ plchldr ];
+    broken = kernel.kernelOlder "5.4" || kernel.kernelAtLeast "6.15";
   };
 }