Revert "EC2: Disable PV support"

This reverts commit fbe6d23624.

this breaks every non-ec2 (non-hvm) system

cc @edolstra

nixos/modules/virtualisation/amazon-options.nix

@@ -12,11 +12,5 @@
     };
   };
 
-  config = {
-    assertions = [
-      { assertion = config.ec2.hvm;
-        message = "Paravirtualized EC2 instances are no longer supported.";
-      }
-    ];
-  };
+  config = {};
 }