mfd: Add GPIOLIB dependency if INTEL_SOC_PMIC is to be enabled

This is needed as the CRC PMIC has support for Panel
enable/diable as gpio which needs 'gpiod_add_lookup_table'
and 'gpiod_remove_lookup_table' from gpiolib. This patch
can be squashed with below commit in topic/crc-pmic branch

    commit 61dd2ca2
    Author: Shobhit Kumar <shobhit.kumar@intel.com>
    Date:   Fri Jun 26 14:32:05 2015 +0530

    mfd: intel_soc_pmic_core: Add lookup table for Panel Control as GPIO
    signal

    On some Intel SoC platforms, the panel enable/disable signals
    are controlled by CRC PMIC. Add those control as a new GPIO in a
    lookup table for gpio-crystalcove chip during CRC driver load

Cc: Lee Jones <lee.jones@linaro.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>