ARM: ux500: remove regulator-compatible usage

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 since the values of the node's
name and the regulator-compatible match for all the regulators.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>