scsi: add a dma_alignment field to the host and host template

scsi: add a dma_alignment field to the host and host template

Get drivers out of the business of having to call the block layer
dma alignment limits helpers themselves.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>