splitting parts of system config

- hardware-configuration.nix separated into kernel-winter.nix and
  filesystem-winter.nix
- kernel.nix split off into kernel-winter.nix

modules/system/kernel-winter.nix

@@ -0,0 +1,22 @@
+{ config, pkgs, ... }: {
+  boot = {
+    loader = {
+      systemd-boot.enable = true;
+      efi.canTouchEfiVariables = true;
+      grub = {
+        enable = true;
+        efiSupport = true;
+        device = "nodev";
+      };
+    };
+    initrd.kernelModules = [ "i915" ];
+    kernelParams = [
+      "amdgpu.gpu_recovery=1"
+      "amdgpu.si_support=1"
+      "radeon.si_support=0"
+      "intel_pstate=passive"
+      "msr.allow_writes=on"
+    ];
+    kernelPackages = pkgs.lib.mkForce (pkgs.linuxPackagesFor pkgs.linux-lava);
+  };
+}