Busy flag was set to true after call to dcd_edpt_xfer().
In some cased it was possible that transfer finished before function
ended.
In this case busy flag could be set to false before it was set to
true.
Then setting it to true after dcd_edpt_xfer() made edpoint busy forever.
This change marks endpoint as busy before transfer is started to
avoid race condition.
For IN endpoints output FIFO is filled in interrupt, therefor before
endpoint is enabled, DIEPTSIZ is set with correct size of packet.
Then endpoint is enabled and FIFO empty interrupt is enabled.
This works fine except for the ZLP. Enabling FIFO empty interrupt
results in interrupt handler being called all the time because
there is nothing to put in the FIFO.
Eventually it ends when IN token is received and empty
packed is transmitted out.
This change does not enable FIFO empty interrupt for ZLP reducing
CPU load.
Queue table has pointers instead of data os_event structs.
This resulted in crashes when elements were put to queue and
overwritten variables that were just after mpool desiged
for queue.
Jerzy Kasenberg