radv/radeonsi/nir: lower 64bit flrp

Fixes a bunch of arb_gpu_shader_fp64 piglit tests for example:

generated_tests/spec/arb_gpu_shader_fp64/execution/built-in-functions/fs-mix-double-double-double.shader_test

Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
2 files changed