block: replace sizeof(rq->cmd) with BLK_MAX_CDB

This is a preparation for changing rq->cmd from the static array to a
pointer.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Boaz Harrosh <bharrosh@panasas.com>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
index fe9df38..68e7f19 100644
--- a/drivers/ide/ide-cd.c
+++ b/drivers/ide/ide-cd.c
@@ -782,7 +782,7 @@
 
 	sector_div(frame, queue_hardsect_size(drive->queue) >> SECTOR_BITS);
 
-	memset(rq->cmd, 0, sizeof(rq->cmd));
+	memset(rq->cmd, 0, BLK_MAX_CDB);
 	rq->cmd[0] = GPCMD_SEEK;
 	put_unaligned(cpu_to_be32(frame), (unsigned int *) &rq->cmd[2]);
 
@@ -1694,7 +1694,7 @@
 	long block = (long)rq->hard_sector / (hard_sect >> 9);
 	unsigned long blocks = rq->hard_nr_sectors / (hard_sect >> 9);
 
-	memset(rq->cmd, 0, sizeof(rq->cmd));
+	memset(rq->cmd, 0, BLK_MAX_CDB);
 
 	if (rq_data_dir(rq) == READ)
 		rq->cmd[0] = GPCMD_READ_10;