drivers: usb: Add nRF52840 USBD driver

* Add usbd_dc_nrfx shim

The shim is based on the previous one usbd_dc_nrf5.
For handling the USBD hardware, tested nrfx_usbd driver from nRF SDK
was used.

Briefly tested examples:
* usb/cdc_acm
* usb/dfu (USB communication only due to flash handling issues)
* usb/hid-mouse
* bluetooth/hci_usb

Signed-off-by: Paweł Zadrożniak <pawel.zadrozniak@nordicsemi.no>
7 files changed