AMD IOMMU: make dma_ops_free_pagetable generic

Impact: change code to free pagetables from protection domains

The dma_ops_free_pagetable function can only free pagetables from
dma_ops domains. Change that to free pagetables of pure protection
domains.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>