mailbox: qcom-apcs: Use device-managed registration API

Get rid of some boilerplate driver removal code by using the newly added
device-managed registration API.

Reviewed-by: Bjorn Andersson <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>
Signed-off-by: Jassi Brar <[e-mail]>

drivers/mailbox/qcom-apcs-ipc-mailbox.c

···
 	apcs->mbox.chans = apcs->mbox_chans;
 	apcs->mbox.num_chans = ARRAY_SIZE(apcs->mbox_chans);
 
-	ret = mbox_controller_register(&apcs->mbox);
+	ret = devm_mbox_controller_register(&pdev->dev, &apcs->mbox);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to register APCS IPC controller\n");
 		return ret;
···
 	struct qcom_apcs_ipc *apcs = platform_get_drvdata(pdev);
 	struct platform_device *clk = apcs->clk;
 
-	mbox_controller_unregister(&apcs->mbox);
 	platform_device_unregister(clk);
 
 	return 0;