Fix Facedancer USB Timeout error

[antoinevg]

This PR does a few things:

• Update libgreat command abort handling to function as intended now that the most recent release fixed the bugs that were preventing it from functioning in a sane manner.
• Resets the endpoint FIFO's before issuing a stall to ensure that we clear the USB peripheral state for future requests.
• Primes the OUT endpoint to receive the host ZLP before writing a libgreat response.
• Shortens the delay in the libgreat moondancer connect verb. This may result in the speed of the interface being reported incorrectly but this bug has been fixed in the upcoming luna-soc 0.3.x release.

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closes #188

[miek]

Works for me!