ARM: multi_v7_defconfig: remove unnecessary CONFIG_GPIOLIB

Commit 38669e04 ("ARM: vexpress: Start
using new Versatile Express infrastructure") introduces a hard
dependency to GPIOLIB for the multi_v7_defconfig:

   ARCH_MULTI_V7 -> ARCH_VEXPRESS -> ARCH_REQUIRE_GPIOLIB -> GPIOLIB

Remove unnecessary explicit CONFIG_GPIOLIB=y from multi_v7_defconfig.

Signed-off-by: Josh Cartwright <josh.cartwright@ni.com>
Signed-off-by: Olof Johansson <olof@lixom.net>