llama-fit-params: fix step size for last device (ggml-org#18415)

Author: JohannesGaessler

src/llama.cpp

@@ -512,6 +512,9 @@ static void llama_params_fit_impl(
             if (mem_high[id] > targets[id]) {
                 assert(ngl_per_device_high[id].n_layer > ngl_per_device[id].n_layer);
                 uint32_t delta = ngl_per_device_high[id].n_layer - ngl_per_device[id].n_layer;
+                if (hp_nex > 0 && size_t(id) == nd - 1) {
+                    delta--;
+                }
                 LLAMA_LOG_DEBUG("%s: start filling device %" PRIu32 ", delta=%" PRIu32 "\n", __func__, id, delta);
                 while (delta > 1) {
                     uint32_t step_size = int64_t(delta) * (targets[id] - mem[id]) / (mem_high[id] - mem[id]);