ac/nir: add pass_tessfactors_by_reg param to hs output lower

ac/nir: add pass_tessfactors_by_reg param to hs output lower

radeonsi won't emit tess factor in the lower pass, need to keep
the output for llvm backend to pass it as parameter. This is used
by radeonsi for an optimization to save LDS write.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16705>