ARM: dts: Remove regulator-compatible usage in exynos4412-trats2

The regulator-compatible property from the regulator DT binding was
deprecated and the correct approach is to use the node's name.

This patch has no functional changes but by not using a deprecated
property, new DTS based on this one will not carry the same issue.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>