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

drivers/char/agp/intel-gtt.c

@@ -20,7 +20,7 @@
 #include <linux/kernel.h>
 #include <linux/pagemap.h>
 #include <linux/agp_backend.h>
-#include <linux/intel-iommu.h>
+#include <linux/iommu.h>
 #include <linux/delay.h>
 #include <asm/smp.h>
 #include "agp.h"
@@ -573,18 +573,15 @@ static void intel_gtt_cleanup(void)
  */
 static inline int needs_ilk_vtd_wa(void)
 {
-#ifdef CONFIG_INTEL_IOMMU
 	const unsigned short gpu_devid = intel_private.pcidev->device;
 
-	/* Query intel_iommu to see if we need the workaround. Presumably that
-	 * was loaded first.
+	/*
+	 * Query iommu subsystem to see if we need the workaround. Presumably
+	 * that was loaded first.
 	 */
-	if ((gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_D_IG ||
-	     gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_M_IG) &&
-	     intel_iommu_gfx_mapped)
-		return 1;
-#endif
-	return 0;
+	return ((gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_D_IG ||
+		 gpu_devid == PCI_DEVICE_ID_INTEL_IRONLAKE_M_IG) &&
+		device_iommu_mapped(&intel_private.pcidev->dev));
 }
 
 static bool intel_gtt_can_wc(void)