Split xeon specific configuration from base

To accomodate the raccoon knights workstation, some of the configuration
pulled by m/common/main.nix has to be removed. To solve it, the xeon
specific parts are placed into m/common/xeon.nix and only the common
configuration is at m/common/base.nix.

Reviewed-by: Aleix Roca Nonell <aleix.rocanonell@bsc.es>

m/common/base.nix

@@ -0,0 +1,19 @@
+{
+  # All machines should include this profile.
+  # Includes the basic configuration for an Intel server.
+  imports = [
+    ./base/agenix.nix
+    ./base/boot.nix
+    ./base/env.nix
+    ./base/fs.nix
+    ./base/hw.nix
+    ./base/net.nix
+    ./base/nix.nix
+    ./base/ntp.nix
+    ./base/rev.nix
+    ./base/ssh.nix
+    ./base/users.nix
+    ./base/watchdog.nix
+    ./base/zsh.nix
+  ];
+}