examples : fix examples/metal (#1920)

Co-authored-by: Iwan Kawrakow <iwan.kawrakow@gmail.com>

examples/metal/metal.cpp

@@ -40,8 +40,10 @@ int main(int argc, char ** argv) {
     // this allocates all Metal resources and memory buffers
     auto * ctx_metal = ggml_metal_init();
 
-    ggml_metal_add_buffer(ctx_metal, "data", ggml_get_mem_buffer(ctx_data), ggml_get_mem_size(ctx_data));
-    ggml_metal_add_buffer(ctx_metal, "eval", ggml_get_mem_buffer(ctx_eval), ggml_get_mem_size(ctx_eval));
+    const size_t max_size_data = ggml_get_max_tensor_size(ctx_data);
+    const size_t max_size_eval = ggml_get_max_tensor_size(ctx_eval);
+    ggml_metal_add_buffer(ctx_metal, "data", ggml_get_mem_buffer(ctx_data), ggml_get_mem_size(ctx_data), max_size_data);
+    ggml_metal_add_buffer(ctx_metal, "eval", ggml_get_mem_buffer(ctx_eval), ggml_get_mem_size(ctx_eval), max_size_eval);
 
     // main
     {