These opcodes where fixed to return an integer instead of a boolean
value some time ago but the documentation for them was not updated
and still talked about a boolean result.
Fixes: b0d4ee520 ('nir/opcodes: Fix up uadd_carry and usub_borrow')
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17372>