drm/exynos: atomic check only enabled crtc states

Since atomic check is called also for disabled crtcs it should skip
mode checking as it can be uninitialized. The patch fixes it.
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_crtc.c

@@ -55,6 +55,9 @@ static int exynos_crtc_atomic_check(struct drm_crtc *crtc,
 {
 	struct exynos_drm_crtc *exynos_crtc = to_exynos_crtc(crtc);
 
+	if (!state->enable)
+		return 0;
+
 	if (exynos_crtc->ops->atomic_check)
 		return exynos_crtc->ops->atomic_check(exynos_crtc, state);