conf: remove unused assignment statement in virSysinfoBaseBoardParseXML

Assigning value 0 to @nboards in success path, that stored value is not used.

src/conf/domain_conf.c

@@ -13089,7 +13089,6 @@ virSysinfoBaseBoardParseXML(xmlXPathContextPtr ctxt,
     *baseBoard = boards;
     *nbaseBoard = nboards;
     boards = NULL;
-    nboards = 0;
     ret = 0;
  cleanup:
     VIR_FREE(boards);