drm/i915/selftests: Pretend to be a gfx pci device

Set the class on our mock pci device to GFX. This should be useful for
utilities like intel-iommu that special case gfx devices.

References: https://bugs.freedesktop.org/show_bug.cgi?id=101080
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170518094638.5469-1-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

drivers/gpu/drm/i915/selftests/mock_gem_device.c

@@ -121,6 +121,7 @@ struct drm_i915_private *mock_gem_device(void)
 		goto err;
 
 	device_initialize(&pdev->dev);
+	pdev->class = PCI_BASE_CLASS_DISPLAY << 16;
 	pdev->dev.release = release_dev;
 	dev_set_name(&pdev->dev, "mock");
 	dma_coerce_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));