ARM: exynos_defconfig: Enable S2MPS11 voltage regulator

S2MPS11 voltage regulator is commonly used on the latest Exynos
boards like SMDK5420, Arndale-Octa, etc. Hence it makes sense to
enable it like S5M8767A voltage regulator.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>