The kernel parameter igfx_off is used by users to disable
DMA remapping for the Intel integrated graphic device. It
was designed for bare metal cases where a dedicated IOMMU
is used for graphic. This doesn't apply to virtual IOMMU
case where an include-all IOMMU is used.  This makes the
kernel parameter work with virtual IOMMU as well.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Suggested-by: NKevin Tian <kevin.tian@intel.com>
Fixes: c0771df8 ("intel-iommu: Export a flag indicating that the IOMMU is used for iGFX.")
Signed-off-by: NLu Baolu <baolu.lu@linux.intel.com>
Tested-by: NZhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>