split CPU and GPU from common/cpu/intel

fix #388

common/gpu/intel.nix

@@ -0,0 +1,15 @@
+{ config, lib, pkgs, ... }:
+
+{
+  boot.initrd.kernelModules = [ "i915" ];
+
+  environment.variables = {
+    VDPAU_DRIVER = lib.mkIf config.hardware.opengl.enable (lib.mkDefault "va_gl");
+  };
+
+  hardware.opengl.extraPackages = with pkgs; [
+    vaapiIntel
+    libvdpau-va-gl
+    intel-media-driver
+  ];
+}