block/md: fix md autodetection

Block ext devt conversion missed md_autodetect_dev() call in
rescan_partitions() leaving md autodetect unable to see partitions.
Fix it.

Signed-off-by: Tejun Heo <[e-mail]>
Cc: Neil Brown <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

fs/partitions/check.c

···
 		}
 #ifdef CONFIG_BLK_DEV_MD
 		if (state->parts[p].flags & ADDPART_FLAG_RAID)
-			md_autodetect_dev(bdev->bd_dev+p);
+			md_autodetect_dev(part_to_dev(part)->devt);
 #endif
 	}
 	kfree(state);