regulator: arizona: Update device tree binding to support Madera CODECs

The Arizona regulator drivers are now also used by the Cirrus Logic
Madera audio CODECs, update the binding document to link to the primary
binding document for these as well as the existing Arizona document.
Signed-off-by: NCharles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

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

@@ -5,7 +5,8 @@ of analogue I/O.
 
 This document lists regulator specific bindings, see the primary binding
 document:
-  ../mfd/arizona.txt
+  For Wolfson Microelectronic Arizona codecs: ../mfd/arizona.txt
+  For Cirrus Logic Madera codecs: ../mfd/madera.txt
 
 Optional properties:
   - wlf,ldoena : GPIO specifier for the GPIO controlling LDOENA