cdrom: revert commit 22a9189 (cdrom: use kmalloced buffers instead of buffers on...

cdrom: revert commit 22a9189 (cdrom: use kmalloced buffers instead of buffers on stack)

The commit 22a9189fd073db3d03a4cf8b8c098aa207602de1 (cdrom: use
kmalloced buffers instead of buffers on stack) is introduced to use
kmalloced buffers for packet commands to avoid stack corruption on non
coherent platforms.

SCSI cdrom uses blk_rq_map_kern, which properly avoids DMA on the
stack by using the bounce buffers. IDE cdrom also has the mechnism to
avoids DMA on the stack. So we don't need this extra complexitiy in
cdrom.c, such as allocating just 8 bytes. The lower layers can handle
it.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Tejun Heo <htejun@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>