iommu/vt-d: Don't apply gfx quirks to untrusted devices

commit 67e8a5b1

 upstream.

Currently, an external malicious PCI device can masquerade the VID:PID
of faulty gfx devices, and thus apply iommu quirks to effectively
disable the IOMMU restrictions for itself.

Thus we need to ensure that the device we are applying quirks to, is
indeed an internal trusted device.

Signed-off-by: Rajat Jain <rajatja@google.com>
Reviewed-by: Ashok Raj <ashok.raj@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20200622231345.29722-4-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
[PG: no quirk_iommu_igfx() in v5.2 - hence drop that chunk.]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>