drm/exynos: IOMMU support should not be selectable by user

If system provides IOMMU feature, Exynos DRM should use it by default,
because the Exynos DRM subdrivers don't work correctly when Exynos IOMMU
driver has been enabled and no IOMMU support has been compiled into Exynos
DRM driver.
Signed-off-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/Kconfig

@@ -12,10 +12,9 @@ config DRM_EXYNOS
 	  If M is selected the module will be called exynosdrm.
 
 config DRM_EXYNOS_IOMMU
-	bool "EXYNOS DRM IOMMU Support"
+	bool
 	depends on DRM_EXYNOS && EXYNOS_IOMMU && ARM_DMA_USE_IOMMU
-	help
-	  Choose this option if you want to use IOMMU feature for DRM.
+	default y
 
 config DRM_EXYNOS_DMABUF
 	bool "EXYNOS DRM DMABUF"