linuxPackages.rtl88x2bu: parallel build

So much faster. Tested at -j48.

pkgs/os-specific/linux/rtl88x2bu/default.nix

···
     mkdir -p "$out/lib/modules/${kernel.modDirVersion}/kernel/net/wireless/"
   '';
 
+  enableParallelBuilding = true;
+
   meta = with lib; {
     description = "Realtek rtl88x2bu driver";
     homepage = "https://github.com/morrownr/88x2bu";