drm/st7735r: Use devm_drm_dev_alloc

Already using devm_drm_dev_init, so very simple replacment.

Aside: There was an oddity in the old code, we allocated priv but in
the error path we've freed priv->dbidev ...
Acked-by: David Lechner <david@lechnology.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: David Lechner <david@lechnology.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200415074034.175360-14-daniel.vetter@ffwll.ch

drivers/gpu/drm/tiny/st7735r.c

@@ -195,21 +195,16 @@ static int st7735r_probe(struct spi_device *spi)
 	if (!cfg)
 		cfg = (void *)spi_get_device_id(spi)->driver_data;
 
-	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
-	if (!priv)
-		return -ENOMEM;
+	priv = devm_drm_dev_alloc(dev, &st7735r_driver,
+				  struct st7735r_priv, dbidev.drm);
+	if (IS_ERR(priv))
+		return PTR_ERR(priv);
 
 	dbidev = &priv->dbidev;
 	priv->cfg = cfg;
 
 	dbi = &dbidev->dbi;
 	drm = &dbidev->drm;
-	ret = devm_drm_dev_init(dev, drm, &st7735r_driver);
-	if (ret) {
-		kfree(dbidev);
-		return ret;
-	}
-	drmm_add_final_kfree(drm, dbidev);
 
 	dbi->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
 	if (IS_ERR(dbi->reset)) {