[SPARC] Mark Niagara3 as VIS3-capable
From SPARC T3 Supplement to the UltraSPARC Architecture 2007 Specification:
> T3 SPARC core has a new 9 stage floating point pipeline and added Fused
> Multiply-Add (FMADD) instruction and VIS 3.0 Instructions compared to
> UltraSPARC T2/T2+.
Reviewers: rorth, s-barannikov, brad0
Reviewed By: s-barannikov
Pull Request: https://github.com/llvm/llvm-project/pull/138399
