ui/cocoa.m: Update to new DisplayChangeListener member names

Commit a93a4a2 changed the names of some fields in DisplayChangeListener
and broke compilation of the cocoa UI. Update to the new names.

Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Andreas Färber <andreas.faerber@web.de>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

ui/cocoa.m

diff --git a/ui/cocoa.m b/ui/cocoa.m
index 2383646..87d2e44 100644
--- a/ui/cocoa.m
+++ b/ui/cocoa.m
@@ -1017,8 +1017,8 @@
     dcl = g_malloc0(sizeof(DisplayChangeListener));
 
     // register vga output callbacks
-    dcl->dpy_update = cocoa_update;
-    dcl->dpy_resize = cocoa_resize;
+    dcl->dpy_gfx_update = cocoa_update;
+    dcl->dpy_gfx_resize = cocoa_resize;
     dcl->dpy_refresh = cocoa_refresh;
 
 	register_displaychangelistener(ds, dcl);