pan/bi: Lower cube map coordinates

We need to do the transform specified in the OpenGL spec ourselves, with
some assistance from the hardware.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7408>
1 file changed