ac/nir: fix nir_intrinsic_shared_atomic_fadd

This was completely broken.

Fixes dEQP-VK.glsl.atomic_operations.add_float32_compute_shared.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6936>
2 files changed