nir/algebraic: coalesce fmod lowering

nir/algebraic: coalesce fmod lowering

As fmod for 16/32/64 bits lowering does the same, let's merge all of
them in a single case.

Fixes dEQP-VK.glsl.builtin.precision_double.mod.compute.* on ACO.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4118>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4118>