iommu/arm-smmu-v3: Put the SVA mmu notifier in the smmu_domain

This removes all the notifier de-duplication logic in the driver and
relies on the core code to de-duplicate and allocate only one SVA domain
per mm per smmu instance. This naturally gives a 1:1 relationship between
SVA domain and mmu notifier.

It is a significant simplication of the flow, as we end up with a single
struct arm_smmu_domain for each MM and the invalidation can then be
shifted to properly use the masters list like S1/S2 do.

Remove all of the previous mmu_notifier, bond, shared cd, and cd refcount
logic entirely.

The logic here is tightly wound together with the unusued BTM
support. Since the BTM logic requires holding all the iommu_domains in a
global ASID xarray it conflicts with the design to have a single SVA
domain per PASID, as multiple SMMU instances will need to have different
domains.

Following patches resolve this by making the ASID xarray per-instance
instead of global. However, converting the BTM code over to this
methodology requires many changes.

Thus, since ARM_SMMU_FEAT_BTM is never enabled, remove the parts of the
BTM support for ASID sharing that interact with SVA as well.

A followup series is already working on fully enabling the BTM support,
that requires iommufd's VIOMMU feature to bring in the KVM's VMID as
well. It will come with an already written patch to bring back the ASID
sharing using a per-instance ASID xarray.

https://lore.kernel.org/linux-iommu/[email protected]/
https://lore.kernel.org/linux-iommu/[email protected]/

Tested-by: Nicolin Chen <[email protected]>
Tested-by: Shameer Kolothum <[email protected]>
Reviewed-by: Nicolin Chen <[email protected]>
Reviewed-by: Michael Shavit <[email protected]>
Reviewed-by: Jerry Snitselaar <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

Author: jgunthorpe