mfd: ucb1400 needs GPIO

ia64 allmodconfig:

In file included from include/linux/ucb1400.h:27,
                 from drivers/mfd/ucb1400_core.c:24:
include/asm-generic/gpio.h: In function `gpio_get_value_cansleep':
include/asm-generic/gpio.h:147: error: implicit declaration of function `gpio_get_value'
include/asm-generic/gpio.h: In function `gpio_set_value_cansleep':
include/asm-generic/gpio.h:153: error: implicit declaration of function `gpio_set_value'
drivers/mfd/ucb1400_core.c: At top level:

Signed-off-by: Samuel Ortiz <sameo@openedhand.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>