s390/dasd: fix possible buffer overflow in copy_pair_show

dasd_copy_relation->entry[] array might be accessed out of bounds if the
loop does not break.

Fixes: a91ff09 ("s390/dasd: add copy pair setup")
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Link: https://lore.kernel.org/r/20221123160719.3002694-5-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/s390/block/dasd_devmap.c

@@ -1954,7 +1954,7 @@ dasd_copy_pair_show(struct device *dev,
 			break;
 		}
 	}
-	if (!copy->entry[i].primary)
+	if (i == DASD_CP_ENTRIES)
 		goto out;
 
 	/* print all secondary */