iommu/amd: Handle IOMMU_DOMAIN_DMA in ops->domain_free call-back

This domain type is not yet handled in the
iommu_ops->domain_free() call-back. Fix that.

Fixes: 0bb6e243 ('iommu/amd: Support IOMMU_DOMAIN_DMA type allocation')
Cc: stable@vger.kernel.org # v4.2+
Signed-off-by: Joerg Roedel <jroedel@suse.de>