vnc: drop display+ws_display from VncDisplay

Nobody cares about those strings, they are only used to check whenever
the vnc server / websocket support is enabled or not.  Add bools for
this and drop the strings.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Gonglei <arei.gonglei@huawei.com>

ui/vnc.h

@@ -158,8 +158,7 @@ struct VncDisplay
     int lsock;
 #ifdef CONFIG_VNC_WS
     int lwebsock;
-    bool websocket;
-    char *ws_display;
+    bool ws_enabled;
 #endif
     DisplaySurface *ds;
     DisplayChangeListener dcl;
@@ -176,7 +175,8 @@ struct VncDisplay
 
     const char *id;
     QTAILQ_ENTRY(VncDisplay) next;
-    char *display;
+    bool enabled;
+    bool is_unix;
     char *password;
     time_t expires;
     int auth;