virgl: remove an incorrect check in virgl_res_needs_flush

virgl: remove an incorrect check in virgl_res_needs_flush

Imagine this

  resource_copy_region(ctx, dst, ..., src, ...);
  transfer_map(ctx, src, 0, PIPE_TRANSFER_WRITE, ...);

at the beginning of a cmdbuf.  We need to flush in transfer_map so
that the transfer is not reordered before the resource copy.  The
check for "vctx->num_draws == 0 && vctx->num_compute == 0" is not
enough.  Removing the optimization entirely.

Because of the more precise resource tracking in the previous
commit, I hope the performance impact is minimized.  We will have to
go with perfect resource tracking, or attempt a more limited
optimization, if there are specific cases we really need to optimize
for.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>