Function safe_arch::add_m128_s

#[must_use]pub fn add_m128_s(a: m128, b: m128) -> m128

This is supported with target feature sse only.

Low lane a + b, other lanes unchanged.

let a = m128::from_array([1.0, 2.0, 3.0, 4.0]);
let b = m128::from_array([5.0, 6.0, 7.0, 8.5]);
let c = add_m128_s(a, b).to_array();
assert_eq!(c, [6.0, 2.0, 3.0, 4.0]);