nir: Recognize and reduce duplicated fsats.
nir: Recognize and reduce duplicated fsats.

No effect on vc4 shader-db.

v2: Rebase to master (no TGSI->NIR present)

Reviewed-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org> (v1)

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler