drm/armada: Use devm_drm_dev_alloc

Also remove the now no longer needed build bug on since that's already
not needed anymore with drmm_add_final_kfree. Conversion to managed
drm_device cleanup is easy, the final drm_dev_put() is already the
last thing in both the bind unbind as in the unbind flow.

Also, this relies on component.c correctly wrapping bind&unbind in
separate devres groups, which it does.
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Cc: Russell King <linux@armlinux.org.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200904143941.110665-2-daniel.vetter@ffwll.ch

drivers/gpu/drm/armada/armada_drv.c

@@ -87,24 +87,13 @@ static int armada_drm_bind(struct device *dev)
 				     "armada-drm"))
 		return -EBUSY;
 
-	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
-	if (!priv)
-		return -ENOMEM;
-
-	/*
-	 * The drm_device structure must be at the start of
-	 * armada_private for drm_dev_put() to work correctly.
-	 */
-	BUILD_BUG_ON(offsetof(struct armada_private, drm) != 0);
-
-	ret = drm_dev_init(&priv->drm, &armada_drm_driver, dev);
-	if (ret) {
-		dev_err(dev, "[" DRM_NAME ":%s] drm_dev_init failed: %d\n",
-			__func__, ret);
-		kfree(priv);
-		return ret;
+	priv = devm_drm_dev_alloc(dev, &armada_drm_driver,
+				  struct armada_private, drm);
+	if (IS_ERR(priv)) {
+		dev_err(dev, "[" DRM_NAME ":%s] devm_drm_dev_alloc failed: %li\n",
+			__func__, PTR_ERR(priv));
+		return PTR_ERR(priv);
 	}
-	drmm_add_final_kfree(&priv->drm, priv);
 
 	/* Remove early framebuffers */
 	ret = drm_fb_helper_remove_conflicting_framebuffers(NULL,
@@ -174,7 +163,6 @@ static int armada_drm_bind(struct device *dev)
  err_kms:
 	drm_mode_config_cleanup(&priv->drm);
 	drm_mm_takedown(&priv->linear);
-	drm_dev_put(&priv->drm);
 	return ret;
 }
 
@@ -194,8 +182,6 @@ static void armada_drm_unbind(struct device *dev)
 
 	drm_mode_config_cleanup(&priv->drm);
 	drm_mm_takedown(&priv->linear);
-
-	drm_dev_put(&priv->drm);
 }
 
 static int compare_of(struct device *dev, void *data)