[AVR] USB send ZLP when needed
[AVR] USB send ZLP when needed

See #5732 #4864 #4138 #3946

majenkotech/Arduino,majenkotech/Arduino,me-no-dev/Arduino-1,me-no-dev/Arduino-1,majenkotech/Arduino,stickbreaker/Arduino,majenkotech/Arduino,majenkotech/Arduino,me-no-dev/Arduino-1,stickbreaker/Arduino,me-no-dev/Arduino-1,me-no-dev/Arduino-1,majenkotech/Arduino,me-no-dev/Arduino-1,stickbreaker/Arduino,me-no-dev/Arduino-1,stickbreaker/Arduino,stickbreaker/Arduino,stickbreaker/Arduino,stickbreaker/Arduino,majenkotech/Arduino,me-no-dev/Arduino-1