ARM: dts: exynos: Bring order in fixed-regulators naming in Midas boards

exynos4412-midas.dtsi is base for galaxy-s3.dtsi and n710x.dts.  All of
them contain fixed regulators named "voltage-regulator-X".  Their
indexes got mixed up while splitting common code in commit c769eaf7
("ARM: dts: exynos: Split Trats2 DTS in preparation for Midas boards").

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>