llama : load MTP tensors only if they are really used (#26296)

* llama : load MTP tensors only if they are really used

* llama : skip loading MTP (if not used) in remaining models that support MTP

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Co-authored-by: Stanisław Szymczyk <sszymczy@gmail.com>

src/llama-model-loader.h

@@ -79,6 +79,7 @@ struct llama_model_loader {
     bool use_direct_io = false;
     bool check_tensors;
     bool no_alloc;
+    bool load_mtp;
 
     llama_files files;
     llama_ftype ftype;
@@ -129,6 +130,7 @@ struct llama_model_loader {
         llama_load_mode load_mode,
         bool check_tensors,
         bool no_alloc,
+        bool load_mtp,
         const llama_model_kv_override * param_overrides_p,
         const llama_model_tensor_buft_override * param_tensor_buft_overrides_p);