ARM: dts: exynos: Convert exynos5250.dtsi to opp-v2 bindings

Convert Exynos5250 to OPP-v2 bindings. This is a preparation to add proper
support for suspend operation point, which cannot be marked in opp-v1.

Cc: <stable@vger.kernel.org> # 4.3.x: cd6f5545: ARM: dts: exynos: Remove "cooling-{min|max}-level" for CPU nodes
Cc: <stable@vger.kernel.org> # 4.3.x: 672f3319: arm: dts: exynos: Add missing cooling device properties for CPUs
Cc: <stable@vger.kernel.org> # 4.3.x
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>