[SCSI] aha152x: use bounce buffer

Cause highmem buffers to be bounced to low memory until this
driver supports highmem addresses.  Otherwise it just oopses
on NULL buffer addresses.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>