cifX device not assigned to INtime shall be ignored by driver

When using INtime for Windows, PCI(e) devices must be manually assigned to be handled either by Windows or INtime.

To detect if a device is not properly assigned to INtime, the structure for PCI devices (PCIDEV) contains a member called bUnusable. Documentation states:

A Boolean flag which indicates whether the PCI device has been assigned to INtime. If this field contains the value TRUE then the device is not available for use by INtime and an attempt to install an interrupt handler for this device will likely fail.

While polling mode would still be possible, the result when two drivers are handling the same device is undefined and should be prohibited by the driver.