drm/tilcdc: Use drm_atomic_helper_resume/suspend()

Use drm_atomic_helper_resume/suspend() and get rid off all the obsolete
register level context restoring code.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_drv.h b/drivers/gpu/drm/tilcdc/tilcdc_drv.h
index 0619c3c..5e645ce 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_drv.h
+++ b/drivers/gpu/drm/tilcdc/tilcdc_drv.h
@@ -65,10 +65,8 @@
 	 */
 	uint32_t max_width;
 
-	/* register contents saved across suspend/resume: */
-	u32 *saved_register;
-	int saved_dpms_state;
-	bool ctx_valid;
+	/* The context for pm susped/resume cycle is stored here */
+	struct drm_atomic_state *saved_state;
 
 #ifdef CONFIG_CPU_FREQ
 	struct notifier_block freq_transition;