rpmsg: Avoid double-free in mtk_rpmsg_register_device

If rpmsg_register_device fails, it will call
mtk_rpmsg_release_device which already frees mdev.

Fixes: 70179969 ("rpmsg: add rpmsg support for mt8183 SCP.")
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200903080547.v3.1.I56cf27cd59f4013bd074dc622c8b8248b034a4cc@changeidSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/rpmsg/mtk_rpmsg.c

@@ -200,7 +200,6 @@ static int mtk_rpmsg_register_device(struct mtk_rpmsg_rproc_subdev *mtk_subdev,
 	struct rpmsg_device *rpdev;
 	struct mtk_rpmsg_device *mdev;
 	struct platform_device *pdev = mtk_subdev->pdev;
-	int ret;
 
 	mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
 	if (!mdev)
@@ -219,13 +218,7 @@ static int mtk_rpmsg_register_device(struct mtk_rpmsg_rproc_subdev *mtk_subdev,
 	rpdev->dev.parent = &pdev->dev;
 	rpdev->dev.release = mtk_rpmsg_release_device;
 
-	ret = rpmsg_register_device(rpdev);
-	if (ret) {
-		kfree(mdev);
-		return ret;
-	}
-
-	return 0;
+	return rpmsg_register_device(rpdev);
 }
 
 static void mtk_register_device_work_function(struct work_struct *register_work)