yaml: fix dead store

conf-yaml-loader.c:391:17: warning: Value stored to 'retval' is never read [deadcode.DeadStores]
                retval = -1;
                ^        ~~
1 warning generated.

src/conf-yaml-loader.c

@@ -388,7 +388,6 @@ static int ConfYamlParse(yaml_parser_t *parser, ConfNode *parent, int inseq, int
             SCLogDebug("event.type=YAML_MAPPING_START_EVENT; state=%d", state);
             if (state == CONF_INCLUDE) {
                 SCLogError("Include fields cannot be a mapping: line %zu", parser->mark.line);
-                retval = -1;
                 goto fail;
             }
             if (inseq) {