regulator: deprecate regulator-compatible DT property

When the bindings for the TPS6586x regulator were being proposed, I
asserted that DT node naming rules for bus child nodes should also be
applied to nodes inside the TPS6586x regulator node itself. In other
words, that each node providing regulator init data should be named
after the type of object it represented ("regulator") and hence that
some other property was required to indicate which regulator the node
described ("regulator-compatible"). In turn this led to multiple nodes
having the same name, thus requiring node names to use a unit address
to make them unique, thus requiring reg properties within the nodes and

However, subsequent discussion indicates that the rules I was asserting
only applies to standardized bus nodes, and within a device's own node,
the binding can basically do anything sane that it wants.

Hence, this change deprecates the register-compatible property, and
instead uses node names to replace this functionality. This greatly
simplifies the device tree content, making them smaller and more legible.

The code is changed such that old device trees continue to work.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>