cleanup: Item_func_opt_neg::negate()

remove redundant method

sql/item_cmpfunc.h

@@ -839,7 +839,6 @@ class Item_func_opt_neg :public Item_bool_func
   Item_func_opt_neg(THD *thd, List<Item> &list):
     Item_bool_func(thd, list), negated(0), pred_level(0) {}
 public:
-  inline void negate() { negated= !negated; }
   inline void top_level_item() { pred_level= 1; }
   bool is_top_level_item() const { return pred_level; }
   Item *neg_transformer(THD *thd)

sql/sql_yacc.yy

@@ -9016,8 +9016,7 @@ predicate:
             Item_func_in *item= new (thd->mem_root) Item_func_in(thd, *$7);
             if (item == NULL)
               MYSQL_YYABORT;
-            item->negate();
-            $$= item;
+            $$= item->neg_transformer(thd);
           }
         | bit_expr BETWEEN_SYM bit_expr AND_SYM predicate
           {
@@ -9031,8 +9030,7 @@ predicate:
             item= new (thd->mem_root) Item_func_between(thd, $1, $4, $6);
             if (item == NULL)
               MYSQL_YYABORT;
-            item->negate();
-            $$= item;
+            $$= item->neg_transformer(thd);
           }
         | bit_expr SOUNDS_SYM LIKE bit_expr
           {