dt-bindings: mfd: da9062: describe buck modes

This patch adds DT description of da9062 buck regulator modes.
Signed-off-by: NChristoph Fritz <chf.fritz@googlemail.com>
Link: https://lore.kernel.org/r/1573652416-9848-4-git-send-email-chf.fritz@googlemail.comSigned-off-by: NMark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/mfd/da9062.txt

@@ -66,6 +66,9 @@ Sub-nodes:
   details of individual regulator device can be found in:
   Documentation/devicetree/bindings/regulator/regulator.txt
 
+  regulator-initial-mode may be specified for buck regulators using mode values
+  from include/dt-bindings/regulator/dlg,da9063-regulator.h.
+
 - rtc : This node defines settings required for the Real-Time Clock associated
   with the DA9062. There are currently no entries in this binding, however
   compatible = "dlg,da9062-rtc" should be added if a node is created.
@@ -96,6 +99,7 @@ Example:
 				regulator-max-microvolt = <1570000>;
 				regulator-min-microamp = <500000>;
 				regulator-max-microamp = <2000000>;
+				regulator-initial-mode = <DA9063_BUCK_MODE_SYNC>;
 				regulator-boot-on;
 			};
 			DA9062_LDO1: ldo1 {