migration: Enable switchover ack capability

Now that switchover ack logic has been implemented, enable the
capability.

Signed-off-by: Avihai Horon <avihaih@nvidia.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Tested-by: YangHang Liu <yanghliu@redhat.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>

migration/options.c

@@ -562,10 +562,6 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp)
                              "'return-path'");
             return false;
         }
-
-        /* Disable this capability until it's implemented */
-        error_setg(errp, "'switchover-ack' is not implemented yet");
-        return false;
     }
 
     return true;