net: qrtr: start MHI channel after endpoit creation

In the Linux kernel, the following vulnerability has been resolved:

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.