drm/msm: Stop using iommu_present()

Even if some IOMMU has registered itself on the platform "bus", that
doesn't necessarily mean it provides translation for the device we
care about. Replace iommu_present() with a more appropriate check.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/480707/
Link: https://lore.kernel.org/r/5ab4f4574d7f3e042261da702d493ee40d003356.1649168268.git.robin.murphy@arm.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/msm_drv.c

@@ -274,7 +274,7 @@ bool msm_use_mmu(struct drm_device *dev)
 	struct msm_drm_private *priv = dev->dev_private;
 
 	/* a2xx comes with its own MMU */
-	return priv->is_a2xx || iommu_present(&platform_bus_type);
+	return priv->is_a2xx || device_iommu_mapped(dev->dev);
 }
 
 static int msm_init_vram(struct drm_device *dev)