mailbox: mtk-cmdq: Use device-managed registration API

Get rid of some boilerplate driver removal code by using the newly added
device-managed registration API.
Signed-off-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NJassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/mtk-cmdq-mailbox.c

@@ -337,7 +337,6 @@ static int cmdq_remove(struct platform_device *pdev)
 {
 	struct cmdq *cmdq = platform_get_drvdata(pdev);
 
-	mbox_controller_unregister(&cmdq->mbox);
 	clk_unprepare(cmdq->clock);
 
 	if (cmdq->mbox.chans)
@@ -524,7 +523,7 @@ static int cmdq_probe(struct platform_device *pdev)
 		cmdq->mbox.chans[i].con_priv = (void *)&cmdq->thread[i];
 	}
 
-	err = mbox_controller_register(&cmdq->mbox);
+	err = devm_mbox_controller_register(dev, &cmdq->mbox);
 	if (err < 0) {
 		dev_err(dev, "failed to register mailbox: %d\n", err);
 		return err;