[SCSI] relax scsi dma alignment

This patch relaxes the default SCSI DMA alignment from 512 bytes to 4
bytes.  I remember from previous discussions that usb and firewire have
sector size alignment requirements, so I upped their alignments in the
respective slave allocs.

The reason for doing this is so that we don't get such a huge amount of
copy overhead in bio_copy_user() for udev.  (basically all inquiries it
issues can now be directly mapped).

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/ata/libata-scsi.c

@@ -824,6 +824,9 @@ static void ata_scsi_sdev_config(struct scsi_device *sdev)
 	 * requests.
 	 */
 	sdev->max_device_blocked = 1;
+
+	/* set the min alignment */
+	blk_queue_update_dma_alignment(sdev->request_queue, ATA_DMA_PAD_SZ - 1);
 }
 
 static void ata_scsi_dev_config(struct scsi_device *sdev,
@@ -878,7 +881,7 @@ int ata_scsi_slave_config(struct scsi_device *sdev)
 	if (dev)
 		ata_scsi_dev_config(sdev, dev);
 
-	return 0;	/* scsi layer doesn't check return value, sigh */
+	return 0;
 }
 
 /**