regulator/mfd: max8998: Document charger regulator

max8998 has a current regulator for control of its charging
current.  Document it.
Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
Link: https://lore.kernel.org/r/BN6PR04MB06600D05B27BAE69970E3C30A3BA0@BN6PR04MB0660.namprd04.prod.outlook.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/mfd/max8998.txt

@@ -73,6 +73,8 @@ number as described in MAX8998 datasheet.
 	- ESAFEOUT1: (ldo19)
 	- ESAFEOUT2: (ld020)
 
+	- CHARGER: main battery charger current control
+
 Standard regulator bindings are used inside regulator subnodes. Check
   Documentation/devicetree/bindings/regulator/regulator.txt
 for more details.
@@ -113,5 +115,11 @@ Example:
 				regulator-always-on;
 				regulator-boot-on;
 			};
+
+			charger_reg: CHARGER {
+				regulator-name = "CHARGER";
+				regulator-min-microamp = <90000>;
+				regulator-max-microamp = <800000>;
+			};
 		};
 	};