libsepol: cil: silence clang analyzer false positive

In cil_tree_print_expr(), "rc < 0" is equivalent to "rc != 0" but
clang's static analyzer does not know about this. Help it.

Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>

libsepol/cil/src/cil_tree.c

@@ -512,7 +512,7 @@ void cil_tree_print_expr(struct cil_list *datum_expr, struct cil_list *str_expr)
 	} else {
 		rc = cil_expr_to_string(str_expr, &expr_str);
 	}
-	if (rc < 0) {
+	if (rc != SEPOL_OK) {
 		cil_log(CIL_INFO, "ERROR)");
 		return;
 	}