virgl: track valid buffer range for transfer sync

virgl: track valid buffer range for transfer sync

virgl_transfer_queue_is_queued was used to avoid flushing.  That
fails when the resource is being accessed by previous cmdbufs but
not the current one.

The new approach of tracking the valid buffer range does not apply
to textures however.  But hopefully it is fine because the goal is
to avoid waiting for this scenario

  glBufferSubData(..., offset, size, data1);
  glDrawArrays(...);
  // append new vertex data
  glBufferSubData(..., offset+size, size, data2);
  glDrawArrays(...);

If glTex(Sub)Image* turns out to be an issue, we will need to track
valid level/layer ranges as well.

v2: update virgl_buffer_transfer_extend as well
v3: do not remove virgl_transfer_queue_is_queued

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Alexandros Frantzis <alexandros.frantzis@collabora.com> (v1)
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org> (v2)