The ST USB code will automatically receive on any
endpoint that is opened but not in the NAK state.
Make sure we set OUT endpoints to NAK initially.
It also happily writes via a NULL pointer in ep->xfer_buff
which writes to address 0x0000_0000. Since address
0x0 is aliased onto the internal flash by the BOOT0/1 pins
and the internal flash is (normally) in the LOCKED state,
this write puts the internal flash into an errored state.
This errored state means that writes to internal flash
are no longer allowed and all further writes fail.
This code was mistakenly tracking the IN (device-to-host)
requests with data stages. It should have been tracking
the OUT (host-to-device) requests with data stages.
This tracking data is important now that CDC is supported.
CDC actually uses OUT requests with data stages whereas HID
does not. This bug only triggered once CDC was enabled.
