virgl: Remove incorrect resource wait condition

Now that we have copy transfers in place, we can remove the incorrect
resource wait condition. Copy transfers and other optimizations minimize
the performance impact of this removal, while providing the correct
behavior.

Signed-off-by: Alexandros Frantzis <alexandros.frantzis@collabora.com>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>

src/gallium/drivers/virgl/virgl_resource.c

@@ -155,19 +155,6 @@ virgl_resource_transfer_prepare(struct virgl_context *vctx,
          flush = true;
    }
 
-   /* XXX This is incorrect and will be removed.  Consider
-    *
-    *   glTexImage2D(..., data1);
-    *   glDrawArrays();
-    *   glFlush();
-    *   glTexImage2D(..., data2);
-    *
-    * readback and flush are both false in the second glTexImage2D call.  The
-    * draw call might end up seeing data2.  Same applies to buffers with
-    * glBufferSubData.
-    */
-   wait = flush || readback;
-
    if (flush)
       vctx->base.flush(&vctx->base, NULL, 0);