mesa/st: Use binding information from the VAO in feedback rendering.

mesa/st: Use binding information from the VAO in feedback rendering.

Use VAO binding information in feedback rendering. In theory
it should reduce the amount of buffer objects scheduled for rendering.
Feedback rendering is implemented in a crude way anyhow, so I do not
expect much gain here. But for the sake of code reuse we should
use the same code for the same task. And finally if feeback rendering
may get improved the array setup is already well done there.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>