usb: device_next: add usbd_device_set_bcd_device()

Add usbd_device_set_bcd_device() for setting the bcdDevice device
descriptor value.

The default bcdDevice is set to the version of Zephyr being used, which may
or may not be what a downstream USB device wants it to be.

Signed-off-by: Henrik Brix Andersen <henrik@brixandersen.dk>