arm: exynos: Enable OPP library support for exynos5440

The OPP library support is needed for exynos5440 cpu frequency
dynamic scaling driver.

Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>