vnc: stop using DisplayState

Rework DisplayStateListener callbacks to not use the DisplayState
any more.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/ui/vnc.h b/ui/vnc.h
index a96485b..58e002e 100644
--- a/ui/vnc.h
+++ b/ui/vnc.h
@@ -150,7 +150,7 @@
     bool websocket;
     char *ws_display;
 #endif
-    DisplayState *ds;
+    DisplaySurface *ds;
     DisplayChangeListener dcl;
     kbd_layout_t *kbd_layout;
     int lock_key_sync;
@@ -248,7 +248,6 @@
 {
     int csock;
 
-    DisplayState *ds;
     DECLARE_BITMAP(dirty[VNC_MAX_HEIGHT], VNC_DIRTY_BITS);
     uint8_t **lossy_rect; /* Not an Array to avoid costly memcpy in
                            * vnc-jobs-async.c */