drivers: udc_nrf: fix enqueue of control IN transfer with length 0

If the direction of the last setup packet is not to the device but to
the host, then the transfer is not a status stage and should be queued.
This is not checked and prevents a zero length control IN transfer to
the host, e.g. used by the DFU class to indicate the end of the upload
process.

Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>