drm/exynos: remove to use ifdef CONFIG_ARM_DMA_USE_IOMMU

If CONFIG_ARM_DMA_USE_IOMMU is disable, CONFIG_DRM_EXYNOS_IOMMU also is
disable. When CONFIG_DRM_EXYNOS_IOMMU is disable,
is_drm_iommu_supported() returns always false, so we can remove to use
ifdef CONFIG_ARM_DMA_USE_IOMMU in is_drm_iommu_supported().
Signed-off-by: NJoonyoung Shim <jy0922.shim@samsung.com>
Tested-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_iommu.h

@@ -29,13 +29,9 @@ void drm_iommu_detach_device(struct drm_device *dev_dev,
 
 static inline bool is_drm_iommu_supported(struct drm_device *drm_dev)
 {
-#ifdef CONFIG_ARM_DMA_USE_IOMMU
 	struct device *dev = drm_dev->dev;
 
 	return dev->archdata.mapping ? true : false;
-#else
-	return false;
-#endif
 }
 
 int drm_iommu_attach_device_if_possible(