dt-bindings: mfd: s2mps11: Add support S2MPU02 PMIC

This patch add documentation for S2MPU02 PMIC device. S2MPU02 has a little
difference from S2MPS11/S2MPS14 PMIC and has LDO[1-28]/Buck[1-7].
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/s2mps11.txt

 
-* Samsung S2MPS11 and S2MPS14 Voltage and Current Regulator
+* Samsung S2MPS11, S2MPS14 and S2MPU02 Voltage and Current Regulator
 
 The Samsung S2MPS11 is a multi-function device which includes voltage and
 current regulators, RTC, charger controller and other sub-blocks. It is
@@ -7,7 +7,8 @@ interfaced to the host controller using an I2C interface. Each sub-block is
 addressed by the host system using different I2C slave addresses.
 
 Required properties:
-- compatible: Should be "samsung,s2mps11-pmic" or "samsung,s2mps14-pmic".
+- compatible: Should be "samsung,s2mps11-pmic" or "samsung,s2mps14-pmic"
+              or "samsung,s2mpu02-pmic".
 - reg: Specifies the I2C slave address of the pmic block. It should be 0x66.
 
 Optional properties:
@@ -81,11 +82,13 @@ as per the datasheet of s2mps11.
 		  - valid values for n are:
 			- S2MPS11: 1 to 38
 			- S2MPS14: 1 to 25
+			- S2MPU02: 1 to 28
 		  - Example: LDO1, LDO2, LDO28
 	- BUCKn
 		  - valid values for n are:
 			- S2MPS11: 1 to 10
 			- S2MPS14: 1 to 5
+			- S2MPU02: 1 to 7
 		  - Example: BUCK1, BUCK2, BUCK9
 
 Example: