minor : add const qualifiers (#2853)

* made the methods const

# Conflicts:
#	examples/convert-llama2c-to-ggml/convert-llama2c-to-ggml.cpp

* made method const

* Update convert-llama2c-to-ggml.cpp

removed write_raw and write_u32

* llama2c : remove misleading const

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

llama.cpp

@@ -4393,7 +4393,7 @@ struct llama_logit_info {
         }
         return min_heap;
     }
-    float probability_from_logit(float logit) {
+    float probability_from_logit(float logit) const {
         return normalizer * std::exp(logit - max_l);
     }
 };