ARM: multi_v7_defconfig: enable MAX77686 PMIC drivers for exynos4412-prime based SoCs

This patch enables the MAX77686 PMIC drivers in the multi_v7_defconfig used
on exynos4412-prime family of SoCs [1]. The exynos4412-prime based boards
are producing the following runtime errors only on the multi_v7_defconfig [2]:

kern.err: deviceless supply vdd_arm not found, using dummy regulator
kern.err: exynos-cpufreq exynos-cpufreq: failed to set cpu voltage to 1287500
kern.err: cpufreq: __target_index: Failed to change cpu frequency: -22

I reviewed the exynos_defconfig, which does not produce these runtime
errors. It was obvious that the exynos_defconfig has the PMIC drivers
enabled, whereas the multi_v7_defconfig does not. This patch has been tested
on a odroid-u2 and a odroid-u3 board. It has resolved the runtime errors.
Therefore, I purpose we enabled these drivers in the multi_v7_defconfig.

[1] http://www.hardkernel.com/main/products/prdt_info.php?g_code=G135270682824
[2] http://storage.armcloud.us/kernel-ci/mainline/v3.18-rc7-48-g7cc78f8/arm-multi_v7_defconfig/lab-tbaker-00/boot-exynos4412-odroidu3.html



Signed-off-by: Tyler Baker <tyler.baker@linaro.org>
Signed-off-by: Olof Johansson <olof@lixom.net>