drm/exynos: Properly propagate return value in drm_iommu_attach_device()

Propagate the proper error codes from the called functions instead of
unconditionally returning 0.
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Merge conflict so merged it manually.
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_dma.c

@@ -61,7 +61,7 @@ static int drm_iommu_attach_device(struct drm_device *drm_dev,
 				struct device *subdrv_dev, void **dma_priv)
 {
 	struct exynos_drm_private *priv = drm_dev->dev_private;
-	int ret;
+	int ret = 0;
 
 	if (get_dma_ops(priv->dma_dev) != get_dma_ops(subdrv_dev)) {
 		DRM_DEV_ERROR(subdrv_dev, "Device %s lacks support for IOMMU\n",
@@ -92,7 +92,7 @@ static int drm_iommu_attach_device(struct drm_device *drm_dev,
 	if (ret)
 		clear_dma_max_seg_size(subdrv_dev);
 
-	return 0;
+	return ret;
 }
 
 /*