gallivm: Fix max const buffer count.

llvmpipe was reporting 32 max const buffers, while sizing its arrays to 16
according to gallivm's #define.

Fixes: 1d35f77228ad ("gallivm,llvmpipe,draw: Support multiple constant buffers.")
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7695>
(cherry picked from commit d90107a2002891ae0f5e9b1ac9ecd8789c9e1969)
2 files changed