radv: Use correct watermark for early loop exit.

The previous check assumed the stack starts at offset=0, which isn't
necessarily true for ray queries.

Note that this didn't cause correctness issues, just made an optimization
not apply. Found when I accidentally made this load-bearing in a
refactor.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20265>

src/amd/vulkan/radv_rt_common.c

@@ -551,7 +551,7 @@ radv_build_ray_traversal(struct radv_device *device, nir_builder *b,
             /* Early exit if we never overflowed the stack, to avoid having to backtrack to
              * the root for no reason. */
             nir_push_if(b, nir_ilt(b, nir_load_deref(b, args->vars.stack),
-                                   nir_imm_int(b, args->stack_stride)));
+                                   nir_imm_int(b, args->stack_base + args->stack_stride)));
             {
                nir_store_var(b, incomplete, nir_imm_bool(b, false), 0x1);
                nir_jump(b, nir_jump_break);