agp/intel: Use per device iommu check

The IOMMU subsystem has already provided an interface to query whether
the IOMMU hardware is enabled for a specific device. This changes the
check from Intel specific intel_iommu_gfx_mapped (globally exported by
the Intel IOMMU driver) to probing the presence of IOMMU on a specific
device using the generic device_iommu_mapped().

This follows commit cca08469 ("drm/i915: Use per device iommu check")
which converted drm/i915 driver to use device_iommu_mapped().

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
Link: https://lore.kernel.org/r/20220514014322.2927339-3-baolu.lu@linux.intel.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>