ARM: dts: exynos: Correct regulator names

Both CPU-freq and dev-freq drivers support proper regulator lookup from
device-tree, so the early introduced hacks for registering main ARM VDD
regulator under 'vdd_arm' name are no longer needed. Similar for devfreq.
Fix this by removing the obsolete comments and changing the regulator
names to the one, which match the schematics and style for the given
board.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>