staging: fieldbus: anybus: Refuse registering drivers without .probe()

A driver without .probe() callback could never bind to a device because
anybus_bus_probe() returned an error for such a driver. So refuse to
register such a useless driver.

Reviewed-by: Sven Van Asbroeck <TheSven73@gmail.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20210505202923.198607-2-u.kleine-koenig@pengutronix.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>