glsl: Remove int64 div/mod lowering.

glsl: Remove int64 div/mod lowering.

Most drivers that can expose GL4 were claiming the cap anyway (llvmpipe,
softpipe, zink, iris, nvc0, radeonsi, r600, freedreno, d3d12), and just
doing lowering in NIR if nessary.

crocus was only claiming the cap for gen8, but the backend compiler
enables NIR lowering regardless.

svga is the only other GL4 driver that didn't set it, and we can just set
the NIR lowering flag.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Acked-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25777>