sense_buffer is used as DMA target and shouldn't be allocated on
stack.  Use ap->sector_buf instead.  This problem is spotted by Chuck
Ebbert.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NChuck Ebbert <cebbert@redhat.com>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>