Configuration interface on EP0

[Børge Strand-Bergesen]

Hi guys, 

I'm working on experimental firmware code where the configuration interface on EP0 can be optionally left out at build time. The reason is to not show up as "unknown device" on computers which have class drivers for the audio part but not for the configuration interface. 

On UAC2 making the config interface optional was quite easy and everything seems to work as expected. But on UAC1 I'm not yet able to do that. The Audio Widget fails to enumerate in UAC1. 

Do you know if there are any special reasons to keep the EP0 interface explicitly in UAC1 descriptors?

The only parameter I've changed is #define NB_INTERFACE which is reduced by 1 as the EP0 interface is commented out of the descriptors. I've done that the same way in the working UAC2 code as in the defunct UAC1 code. 

Thanks,

Børge