siox: Use bus_type functions for probe, remove and shutdown

The eventual goal is to get rid of the callbacks in struct
device_driver.

Tested-by: Thorsten Scherer <t.scherer@eckelmann.de>
Acked-by: Thorsten Scherer <t.scherer@eckelmann.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20201125093106.240643-2-u.kleine-koenig@pengutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>