Disallow both CMSIS-DAP v1 and v2 to be opened simultaneously

In interface firmware configurations where both CMSIS-DAP v1 and v2 USB interfaces are available, there is a possibility that the user could open both CMSIS-DAP interfaces concurrently. This will, of course, cause unpredictable behaviour.

A real world example is with multicore debug using Keil µVision. If starting a debug session in one µVision instance with the CMSIS-DAP v1 interface, and the CMSIS-DAP v2 interface is selected in the setup dialog of another µVision instance, then the debug connection in the first is lost. The same happens the other way around (debug session with CMSIS-DAPv2 and setup dialog with CMSIS-DAPv1).

The solution is to disallow simultaneous opening of both CMSIS-DAP interfaces. The actual mechanism used to disable a CMSIS-DAP interface needs to be investigated.