Dream Pico Port locks up using new API and flycast

[Tails86]

To reproduce:

• Open flycast from dev branch on Windows with a DreamPicoPort connected, 1 controller inserted into A with VMU, using real memory
• Open Sonic Adventure and wait for initial read of VMU
• Press L+R+Start and select Close Game
• Relaunch Sonic Adventure
• DreamPicoPort is now locked up, and flycast can only be completely closed through the Task Manager (window will disappear after clicking X, but it's still running)

[Tails86]

I have a hunch that USB communication stopped just as DPP was receiving or transmitting data. Maybe this caused a USB STALL and locked up the device.

[Tails86]

I think this issue was because I was playing around with a developmental build where I was messing with the USB endpoint. Something seemed off until I reflashed the firmware

[Tails86]

Nope, this is definitely an issue. Original comment edited with the steps needed to reproduce.

[Tails86]

I don't experience this issue using the latest release of flycast, only on the dev branch. This is definitely because of the new API.

[Tails86]

WebUsbInterface::vendorWrite() is locking up because it looks like tud_vendor_n_write() is not able to write any data. I'm guessing there is a STALL condition on the IN endpoint that is not being cleared?

[Tails86]

Along with this fix, the DreamPicoPort-API needs to be setup to automatically clear the stall or else communication will never proceed from this point. The libusb implementation should be doing that already. The WinRT implementation is not.