[SCSI] dpt_i2o: driver is only 32 bit so don't set 64 bit DMA mask

This fixes a potential corruption bug where the truncation would cause
reading or writing to the wrong memory area on machines with >4GB of
main memory.

Cc: Stable Kernel Tree <stable@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>