mm: use zone_is_initialized() instead of if(zone->wait_table)

Use "zone_is_initialized()" instead of "if (zone->wait_table)".
Simplify the code, no functional change.

Signed-off-by: Xishi Qiu <[e-mail]>
Cc: Cody P Schafer <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/memory_hotplug.c

···
 
 	zone = &pgdat->node_zones[0];
 	for (; zone < pgdat->node_zones + MAX_NR_ZONES - 1; zone++) {
-		if (zone->wait_table) {
+		if (zone_is_initialized(zone)) {
 			nr_pages = zone->wait_table_hash_nr_entries
 				* sizeof(wait_queue_head_t);
 			nr_pages = PAGE_ALIGN(nr_pages) >> PAGE_SHIFT;