nak/mark_lcssa_invariants: Invalidate divergence

Preserving this was resulting in validation errors like:
error: def->loop_invariant == BITSET_TEST(loop_invariance, def->index) (../src/compiler/nir/nir_validate.c:1890)

Fixes: 1d6082bf56 ("nouveau: switch to nir_metadata_divergence")
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36415>
1 file changed