xen/arm: smmuv1: Keep track of S2CR state

xen/arm: smmuv1: Keep track of S2CR state

Backport commit 8e8b203eabd8b9e96d02d6339e4abce3e5a7ea4b
"iommu/arm-smmu: Keep track of S2CR state" from the Linux kernel.

This patch is the preparatory work to fix the stream match conflict
when two devices have the same stream-id.

Original commit message:
    iommu/arm-smmu: Keep track of S2CR state

    Making S2CRs first-class citizens within the driver with a high-level
    representation of their state offers a neat solution to a few problems:

    Firstly, the information about which context a device's stream IDs are
    associated with is already present by necessity in the S2CR. With that
    state easily accessible we can refer directly to it and obviate the need
    to track an IOMMU domain in each device's archdata (its earlier purpose
    of enforcing correct attachment of multi-device groups now being handled
    by the IOMMU core itself).

    Secondly, the core API now deprecates explicit domain detach and expects
    domain attach to move devices smoothly from one domain to another; for
    SMMUv2, this notion maps directly to simply rewriting the S2CRs assigned
    to the device. By giving the driver a suitable abstraction of those
    S2CRs to work with, we can massively reduce the overhead of the current
    heavy-handed "detach, free resources, reallocate resources, attach"
    approach.

    Thirdly, making the software state hardware-shaped and attached to the
    SMMU instance once again makes suspend/resume of this register group
    that much simpler to implement in future.

    Signed-off-by: Robin Murphy <robin.murphy@arm.com>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Rahul Singh <rahul.singh@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>
Acked-by: Julien Grall <jgrall@amazon.com>