llama : fix struct decl (ggml-org#2790)

Author: MarcusDunn

llama.h

@@ -485,7 +485,7 @@ extern "C" {
     // (e.g. beams[0]) as they will be removed (shifted) from all beams in all subsequent callbacks.
     // These pointers are valid only during the synchronous callback, so should not be saved.
     struct llama_beams_state {
-        llama_beam_view * beam_views;
+        struct llama_beam_view * beam_views;
         size_t n_beams;               // Number of elements in beam_views[].
         size_t common_prefix_length;  // Current max length of prefix tokens shared by all beams.
         bool last_call;               // True iff this is the last callback invocation.