radv/winsys: fix creating the BO list for virtual buffers

When the number of unique BO is 0, we optimize the list creation
by copying all buffers of the current CS directly into it. But
this is only valid if the CS doesn't have virtual buffers,
otherwise they are not added and hw might report VM faults.

This fixes VM faults with:
dEQP-VK.sparse_resources.image_sparse_binding.2d.rgba8ui.1024_128_1

CC: <mesa-stable@lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
(cherry picked from commit d27e1584)