Figure out "can't modify CPUCS: Protocol error fx2" error

[mithro]

After loading the CDC firmware, sometimes you can't load the firmware again. Instead fxload dies with the error;
can't modify CPUCS: Protocol error fx2

[mithro]

See this code for possible more information https://github.com/libusb/libusb/blob/master/examples/ezusb.c#L172