radv: fix using FS sample shading if the linker optimized inputs away
During NIR linking, constant varyings might be moved to the next
stage and the sample qualifier removed.
shader_info::uses_sample_shading remembers if the sample qualifier
was used before optimizations.
No fossils-db changes on Sienna Cichlid.
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/7892>