ARM: dts: db8500: add property "regulator-compatible" regulator node

Device's regulator matches their hardware counterparts with the
property "regulator-compatible" of each child regulator node in
place of the child node name.
Add the property "regulator-compatible" for each regulator with
their hardware counterpart's name.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>