common/cpu/intel: add vaapi/vdpau drivers

I've tested this to work on MacBookAir4,1 and I'm going to deploy it
to MacBookAir6,2 today and Lenovo ThinkPad X230 in a week from now.
Also, cleaned up Lenovo ThinkPad X230 profile.

common/cpu/intel/default.nix

@@ -1,4 +1,12 @@
+{ lib, pkgs, ... }:
+
 {
-  hardware.cpu.intel.updateMicrocode = true;
+  hardware.cpu.intel.updateMicrocode = lib.mkDefault true;
   services.xserver.videoDrivers = [ "intel" ];
+
+  hardware.opengl.extraPackages = with pkgs; [
+    vaapiIntel
+    vaapiVdpau
+    libvdpau-va-gl
+  ];
 }