regulator: Update regulator_register() API signature in Documentation

commit c172708d "regulator: core: Use a struct to pass in regulator runtime
configuration" changed the regulator_register() API signature.

Update the Documentation accordingly to reflect the change in the function
signature.
Signed-off-by: NAxel Lin <axel.lin@gmail.com>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

Documentation/power/regulator/regulator.txt

@@ -11,8 +11,7 @@ Registration
 Drivers can register a regulator by calling :-
 
 struct regulator_dev *regulator_register(struct regulator_desc *regulator_desc,
-	struct device *dev, struct regulator_init_data *init_data,
-	void *driver_data, struct device_node *of_node);
+					 const struct regulator_config *config);
 
 This will register the regulators capabilities and operations to the regulator
 core.