regulator: Change regulator-coupled-max-spread property

Redefine binding for regulator-coupled-max-spread property in a way that
max-spread values are defined per regulator couple instead of defining
single max-spread for the whole group of coupled regulators.

With that change the following regulators coupling configuration will be
possible:

regA: regulatorA {
	regulator-coupled-with = <&regB &regC>;
	regulator-coupled-max-spread = <100000 300000>;
};

regB: regulatorB {
	regulator-coupled-with = <&regA &regC>;
	regulator-coupled-max-spread = <100000 200000>;
};

regC: regulatorC {
	regulator-coupled-with = <&regA &regB>;
	regulator-coupled-max-spread = <300000 200000>;
};

Note that the regulator-coupled-max-spread property does not have any
users yet, hence it's okay to change the binding.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/regulator.txt

@@ -79,8 +79,9 @@ Optional properties:
 - regulator-coupled-with: Regulators with which the regulator
   is coupled. The linkage is 2-way - all coupled regulators should be linked
   with each other. A regulator should not be coupled with its supplier.
-- regulator-coupled-max-spread: Max spread between voltages of coupled regulators
-  in microvolts.
+- regulator-coupled-max-spread: Array of maximum spread between voltages of
+  coupled regulators in microvolts, each value in the array relates to the
+  corresponding couple specified by the regulator-coupled-with property.
 
 Deprecated properties:
 - regulator-compatible: If a regulator chip contains multiple