vaapivideomemory: Store surface allocation flags.

Store surface allocation flags passed to the vaapi allocator in
GObject's qdata, because it might be used by the vaapivideobufferpool
when recreating the allocator given any resolution change.

gst/vaapi/gstvaapivideomemory.c

@@ -987,6 +987,9 @@ gst_vaapi_video_allocator_new (GstVaapiDisplay * display,
     return NULL;
   }
 
+  gst_allocator_set_vaapi_video_info (GST_ALLOCATOR_CAST (allocator),
+      alloc_info, surface_alloc_flags);
+
   return GST_ALLOCATOR_CAST (allocator);
 }