Bluetooth: Don't initialize msft/aosp when using user channel

A race condition is triggered when usermode control is given to
userspace before the kernel's MSFT query responds, resulting in an
unexpected response to userspace's reset command.

Issue can be observed in btmon:

< HCI Command: Vendor (0x3f|0x001e) plen 2                    #3 [hci0]
        05 01                                            ..
@ USER Open: bt_stack_manage (privileged) version 2.22  {0x0002} [hci0]
< HCI Command: Reset (0x03|0x0003) plen 0                     #4 [hci0]
> HCI Event: Command Complete (0x0e) plen 5                   #5 [hci0]
      Vendor (0x3f|0x001e) ncmd 1
	Status: Command Disallowed (0x0c)
	05                                               .
> HCI Event: Command Complete (0x0e) plen 4                   #6 [hci0]
      Reset (0x03|0x0003) ncmd 2
	Status: Success (0x00)
Reviewed-by: NAbhishek Pandit-Subedi <abhishekpandit@chromium.org>
Reviewed-by: NSonny Sasaka <sonnysasaka@chromium.org>
Signed-off-by: NJesse Melhuish <melhuishj@chromium.org>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

net/bluetooth/hci_sync.c

@@ -3887,8 +3887,10 @@ int hci_dev_open_sync(struct hci_dev *hdev)
 	    hci_dev_test_flag(hdev, HCI_VENDOR_DIAG) && hdev->set_diag)
 		ret = hdev->set_diag(hdev, true);
 
-	msft_do_open(hdev);
-	aosp_do_open(hdev);
+	if (!hci_dev_test_flag(hdev, HCI_USER_CHANNEL)) {
+		msft_do_open(hdev);
+		aosp_do_open(hdev);
+	}
 
 	clear_bit(HCI_INIT, &hdev->flags);
 
@@ -4031,8 +4033,10 @@ int hci_dev_close_sync(struct hci_dev *hdev)
 
 	hci_sock_dev_event(hdev, HCI_DEV_DOWN);
 
-	aosp_do_close(hdev);
-	msft_do_close(hdev);
+	if (!hci_dev_test_flag(hdev, HCI_USER_CHANNEL)) {
+		aosp_do_close(hdev);
+		msft_do_close(hdev);
+	}
 
 	if (hdev->flush)
 		hdev->flush(hdev);