gallivm/nir: lower frexp/ldexp

Fixes:
dEQP-VK.glsl.builtin.precision.frexp*
dEQP-VK.glsl.builtin.precision.ldexp*

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6381>
2 files changed