md/raid5: use bio_end_sector to calculate last_sector

Use the common way to get last_sector.
Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

drivers/md/raid5.c

@@ -5499,7 +5499,7 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi)
 		return;
 
 	logical_sector = bi->bi_iter.bi_sector & ~((sector_t)STRIPE_SECTORS-1);
-	last_sector = bi->bi_iter.bi_sector + (bi->bi_iter.bi_size>>9);
+	last_sector = bio_end_sector(bi);
 
 	bi->bi_next = NULL;