iommu/amd: Initialize dma-ops domains with 3-level page-table

A two-level page-table can map up to 1GB of address space.
With the IOVA allocator now in use, the allocated addresses
are often more closely to 4G, which requires the address
space to be increased much more often. Avoid that by using a
three-level page-table by default.

Signed-off-by: Joerg Roedel <jroedel@suse.de>