iommu: Use flush queue capability

It remains really handy to have distinct DMA domain types within core
code for the sake of default domain policy selection, but we can now
hide that detail from drivers by using the new capability instead.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Jerry Snitselaar <jsnitsel@redhat.com> # amd, intel, smmu-v3
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/1c552d99e8ba452bdac48209fa74c0bdd52fd9d9.1683233867.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>