iommu/vt-d: Move intel_iommu info from struct intel_svm to struct intel_svm_dev

'struct intel_svm' is shared by all devices bound to a give process,
but records only a single pointer to a 'struct intel_iommu'. Consequently,
cache invalidations may only be applied to a single DMAR unit, and are
erroneously skipped for the other devices.

In preparation for fixing this, rework the structures so that the iommu
pointer resides in 'struct intel_svm_dev', allowing 'struct intel_svm'
to track them in its device list.

Fixes: 1c4f88b7

 ("iommu/vt-d: Shared virtual address in scalable mode")
Cc: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Raj Ashok <ashok.raj@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Reported-by: Guo Kaijie <Kaijie.Guo@intel.com>
Reported-by: Xin Zeng <xin.zeng@intel.com>
Signed-off-by: Guo Kaijie <Kaijie.Guo@intel.com>
Signed-off-by: Xin Zeng <xin.zeng@intel.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Tested-by: Guo Kaijie <Kaijie.Guo@intel.com>
Cc: stable@vger.kernel.org # v5.0+
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/1609949037-25291-2-git-send-email-yi.l.liu@intel.com
Signed-off-by: Will Deacon <will@kernel.org>