MINOR: acl: remove the use_count in acl keywords

use_cnt is not used at all anymore, let's get rid of it.
diff --git a/include/types/acl.h b/include/types/acl.h
index e1d0f12..9ea0cfa 100644
--- a/include/types/acl.h
+++ b/include/types/acl.h
@@ -168,7 +168,6 @@
 	int (*match)(struct sample *smp, struct acl_pattern *pattern);
 	/* must be after the config params */
 	struct sample_fetch *smp; /* the sample fetch we depend on */
-	int use_cnt;
 };
 
 /*
diff --git a/src/acl.c b/src/acl.c
index 9c75b97..d1c149f 100644
--- a/src/acl.c
+++ b/src/acl.c
@@ -928,7 +928,6 @@
 
 	if (expr->args != empty_arg_list)
 		free(expr->args);
-	expr->kw->use_cnt--;
 	return expr;
 }
 
@@ -1052,7 +1051,6 @@
 	}
 
 	expr->kw = aclkw;
-	aclkw->use_cnt++;
 	LIST_INIT(&expr->patterns);
 	expr->pattern_tree = EB_ROOT_UNIQUE;
 	expr->parse = aclkw->parse;