gpio: 74x164: use spi_get_drvdata() and spi_set_drvdata()

Use the wrapper functions for getting and setting the driver data
using spi_device instead of using dev_{get|set}_drvdata with
&spi->dev, so we can directly pass a struct spi_device.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>