mm: fix typo in struct pglist_data code comment

change "stat" to "start".

Link: https://lkml.kernel.org/r/20221207074011.GA151242@cloud
Fixes: c959924b ("memory tiering: adjust hot threshold automatically")
Signed-off-by: NWang Yong <yongw.kernel@gmail.com>
Reviewed-by: N"Huang, Ying" <ying.huang@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

include/linux/mmzone.h

@@ -1200,7 +1200,7 @@ typedef struct pglist_data {
 	/* start time in ms of current promote threshold adjustment period */
 	unsigned int nbp_th_start;
 	/*
-	 * number of promote candidate pages at stat time of current promote
+	 * number of promote candidate pages at start time of current promote
 	 * threshold adjustment period
 	 */
 	unsigned long nbp_th_nr_cand;