nir: Add algebraic opt for int comparisons with identical operands.
nir: Add algebraic opt for int comparisons with identical operands.

No change on shader-db on i965.

v2: Reword the comment due to feedback from Erik Faye-Lund

Reviewed-by: Connor Abbott <71178acffcc112b21e5858656e5751f5e4aa9364@gmail.com> (v1)
Reviewed-by: Jason Ekstrand <b186559eaedf698788888c8a2559b4efb4db10d6@intel.com> (v1)

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler