Add warning dialog to DSHMC when device restart failed

[nefarius]

The Apply button in DSHMC doesn't actually save/apply the changed settings, that always happens instantaneous, the Apply button requests the affected device to be restarted, so that the changes actually become live. This does not always work; if processes/games hold an open handle to the device, the SetupAPI/PnP-subsystem will simply fail to satisfy the restart request and the device needs to be unplugged/power-cycled instead.

Add an informative dialog instead of swallowing the error.