blk_queue_update_dma_alignment — update dma length and memory alignment
the request queue for the device
alignment mask
update required memory and length aligment for direct dma transactions. If the requested alignment is larger than the current alignment, then the current queue alignment is updated to the new value, otherwise it is left alone. The design of this is to allow multiple objects (driver, device, transport etc) to set their respective alignments without having them interfere.