radeonsi: remove si_shader_output_values::index
radeonsi: remove si_shader_output_values::index

It's redundant now.

It led to a simplification in si_llvm_emit_streamout, because outidx == reg.

Reviewed-by: Michel Dänzer <242b79f0804cf52679d58f27ed754158c1323c75@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler