regulator: dt: regulator-name is required property

These two drivers fail to probe if no name is provided. For details see:
https://www.spinics.net/lists/kernel/msg2457515.html

Signed-off-by: Harald Geyer <harald@ccbib.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/fixed-regulator.txt

@@ -2,6 +2,7 @@ Fixed Voltage regulators
 
 Required properties:
 - compatible: Must be "regulator-fixed";
+- regulator-name: Defined in regulator.txt as optional, but required here.
 
 Optional properties:
 - gpio: gpio to use for enable control

Documentation/devicetree/bindings/regulator/gpio-regulator.txt

@@ -2,6 +2,8 @@ GPIO controlled regulators
 
 Required properties:
 - compatible		: Must be "regulator-gpio".
+- regulator-name	: Defined in regulator.txt as optional, but required
+			  here.
 - states		: Selection of available voltages and GPIO configs.
                           if there are no states, then use a fixed regulator