There is a pair of USB requests ( GS_USB_BREQ_GET_USER_ID and
_SET_USER_ID) that is not supported by the linux driver, and not used by
any known software :
https://github.com/candle-usb/candleLight_fw/issues/91
Since the firmware returns a unique serial #, there doesn't appear to be
any use case for assigning a user ID. Using a whole flash page for that
purpose can be wasteful on bigger targets .
This removes all the relevant code and adjusts the linker scripts
accordingly.