drm/exynos: remove unnecessary checking to support iommu

Already drm_iommu_attach_device and drm_iommu_detach_device check
whether support iommu internally, so we don't have to call
is_drm_iommu_supported before call them.

Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
diff --git a/drivers/gpu/drm/exynos/exynos_drm_iommu.c b/drivers/gpu/drm/exynos/exynos_drm_iommu.c
index d4ec746..4c2ec1b 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_iommu.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_iommu.c
@@ -87,10 +87,8 @@
 	struct device *dev = drm_dev->dev;
 	int ret;
 
-	if (!dev->archdata.mapping) {
-		DRM_ERROR("iommu_mapping is null.\n");
-		return -EFAULT;
-	}
+	if (!dev->archdata.mapping)
+		return 0;
 
 	subdrv_dev->dma_parms = devm_kzalloc(subdrv_dev,
 					sizeof(*subdrv_dev->dma_parms),
@@ -148,13 +146,10 @@
 int drm_iommu_attach_device_if_possible(struct exynos_drm_crtc *exynos_crtc,
 			struct drm_device *drm_dev, struct device *subdrv_dev)
 {
-	int ret = 0;
-
 	if (is_drm_iommu_supported(drm_dev)) {
 		if (exynos_crtc->ops->clear_channels)
 			exynos_crtc->ops->clear_channels(exynos_crtc);
-		return drm_iommu_attach_device(drm_dev, subdrv_dev);
 	}
 
-	return ret;
+	return drm_iommu_attach_device(drm_dev, subdrv_dev);
 }