can: gs_usb: document GS_CAN_FEATURE_BERR_REPORTING

Document the new feature ("GS_CAN_FEATURE_BERR_REPORTING") that
indicates that the bus error reporting in the CAN controller can
switched on and off with the GS_CAN_MODE_BERR_REPORTING mode bit in
the GS_USB_BREQ_MODE control message.

Signed-off-by: Jeroen Hofstee <jhofstee@victronenergy.com>
Link: https://lore.kernel.org/all/20221019221016.1659260-5-mkl@pengutronix.de


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>