iommu: Add missing new line for dma type

So that all types are printed in the same format.

Fixes: c52c72d3 ("iommu: Add sysfs attribyte for domain type")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>