Many Intel processors (and BIOSes) have invalid IOMMU configuration for
IGFX, which cause multiple problems - from screen glitches, to system
hang.
Since IGFX currently is still in dom0 (isn't isolated from other system
components), disabling IOMMU for it doesn't lower overall security.
When GUI domain will be implemented, we need to re-enable IOMMU here and
hope hardware manufacturers will fix it in the meantime.
FixesQubesOS/qubes-issues#2836