mfd: ucb1400: Pass ucb1400-gpio data through ac97 bus

Cc: Jean Delvare <jdelvare@suse.de>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>