ac/nir: implement nir_op_fsat

With fmed3 if available, otherwise fallback to fmin/fmax.

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/6932>
3 files changed