conf: Fix error message to use correct parameter

Fix a cut-n-paste error from commit id '35eecdde' where the previous
check for max_sectors seems to have been copied, but the error message
parameter not updated to be ioeventfd

src/conf/domain_conf.c

@@ -7985,7 +7985,7 @@ virDomainControllerDefParseXML(xmlNodePtr node,
     if (ioeventfd &&
         (def->ioeventfd = virTristateSwitchTypeFromString(ioeventfd)) < 0) {
         virReportError(VIR_ERR_XML_ERROR,
-                       _("Malformed 'ioeventfd' value %s'"), max_sectors);
+                       _("Malformed 'ioeventfd' value %s'"), ioeventfd);
         goto error;
     }