net: qrtr: start MHI channel after endpoit creation

MHI channel may generates event/interrupt right after enabling.
It may leads to 2 race conditions issues.

1)
Such event may be dropped by qcom_mhi_qrtr_dl_callback() at check:

if (!qdev || mhi_res->transaction_status)
return;

Because dev_set_drvdata(&mhi_dev->dev, qdev) may be not performed at
this moment. In this situation qrtr-ns will be unable to enumerate
services in device.
---------------------------------------------------------------

2)
Such event may come at the moment after dev_set_drvdata() and
before qrtr_endpoint_register(). In this case kernel will panic with
accessing wrong pointer at qcom_mhi_qrtr_dl_callback():

rc = qrtr_endpoint_post(&qdev->ep, mhi_res->buf_addr,
mhi_res->bytes_xferd);

Because endpoint is not created yet.
--------------------------------------------------------------
So move mhi_prepare_for_transfer_autoqueue after endpoint creation
to fix it.

Fixes: a2e2cc0dbb11 ("net: qrtr: Start MHI channels during init")
Signed-off-by: Maxim Kochetkov <[e-mail]>
Reviewed-by: Hemant Kumar <[e-mail]>
Reviewed-by: Manivannan Sadhasivam <[e-mail]>
Reviewed-by: Loic Poulain <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/qrtr/mhi.c

···
 	struct qrtr_mhi_dev *qdev;
 	int rc;
 
-	/* start channels */
-	rc = mhi_prepare_for_transfer_autoqueue(mhi_dev);
-	if (rc)
-		return rc;
-
 	qdev = devm_kzalloc(&mhi_dev->dev, sizeof(*qdev), GFP_KERNEL);
 	if (!qdev)
 		return -ENOMEM;
···
 	rc = qrtr_endpoint_register(&qdev->ep, QRTR_EP_NID_AUTO);
 	if (rc)
 		return rc;
+
+	/* start channels */
+	rc = mhi_prepare_for_transfer_autoqueue(mhi_dev);
+	if (rc) {
+		qrtr_endpoint_unregister(&qdev->ep);
+		return rc;
+	}
 
 	dev_dbg(qdev->dev, "Qualcomm MHI QRTR driver probed\n");