siox: Add helper macro to simplify driver registration

Add more helper macros for trivial driver init cases, similar to the
already existing module_platform_driver() or module_i2c_driver().

This helps to reduce driver init boilerplate.

Signed-off-by: Enrico Weigelt <info@metux.net>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>