iommu: Add quirk for Intel graphic devices in map_sg

Combining the sg segments exposes a bug in the Intel i915 driver which
causes visual artifacts and the screen to freeze. This is most likely
because of how the i915 handles the returned list. It probably doesn't
respect the returned value specifying the number of elements in the list
and instead depends on the previous behaviour of the Intel iommu driver
which would return the same number of elements in the output list as in
the input list.

[ This has been fixed in the i915 tree, but we agreed to carry this fix
  temporarily in the iommu tree and revert it before 5.11 is released:

  https://lore.kernel.org/linux-iommu/20201103105442.GD22888@8bytes.org/



  -- Will ]

Signed-off-by: Tom Murphy <murphyt7@tcd.ie>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Tested-by: Logan Gunthorpe <logang@deltatee.com>
Link: https://lore.kernel.org/r/20201124082057.2614359-5-baolu.lu@linux.intel.com


Signed-off-by: Will Deacon <will@kernel.org>