SCSI: Introduce dma_boundary parameter
James Bottomley authored
From: Jens Axboe <axboe@suse.de>

The block layer includes the ability to avoid merging if the merged
segment would cross a particular boundary (by default, this boundary
is set to 4GB which is the PCI DAC requirement).

This patch makes the boundary tunable in SCSI for drivers that need
different ones (usually because of card constraints)
65a803ab