gallium/util: fix texture-coordinates for stencil-fallback

Set up texture coordinates for the stencil-fallback blit code. This
worked in the orignal NIR code, but accidentally broke when rewriting to
use TGSI, and my test-case had a constant colored stencil buffer.

Fixes: e8a40715a8b ("gallium/util: add blitter-support for stencil-fallback")
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6898>
1 file changed