mtip32xx: also set max_segment_size in the device

If we only set the max_segment_size on the queue an IOMMU merge might
create bigger segments again, so limit the IOMMU merges as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>