memory-hotplug: build zonelist if a zone is populated after onlining pages

memory-hotplug: build zonelist if a zone is populated after onlining pages

After "memory-hotplug: allocate zone's pcp before onlining pages", we
build zone list before onlining pages to allocate zone's pcp.  But the
zone doesn't have pages before onlining pages, and the zone is not in
zonelist, so we still need to build zonelist after onlining pages.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jiang Liu <liuj97@gmail.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>