nir/lower_robust_access: fix robustness with atomic swap

this was missed in the original v3d pass, and then the common code port
inherited the bug. (so strictly this fix "should" be backported even farther
back but it won't apply before the Fixes here, and I don't think we do LTS that
far back anyway).

in theory this should fix a corner case with robustness on the gl (but not
vulkan, at least for apple) drivers on broadcom & apple.

Fixes: f0fb8d05e3 ("nir: Add nir_lower_robust_access pass")
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32907>

src/compiler/nir/nir_lower_robust_access.c

@@ -191,6 +191,7 @@ lower(nir_builder *b, nir_intrinsic_instr *intr, void *_opts)
       lower_buffer_store(b, intr);
       return true;
    case nir_intrinsic_ssbo_atomic:
+   case nir_intrinsic_ssbo_atomic_swap:
       lower_buffer_atomic(b, intr);
       return true;