regulator: max77686: Make max77686_enable() static.

This patch fixes a sparse warning. Since max77686_enable() is a callback,so it
should be static.
Signed-off-by: Yadwinder Singh Brar <yadi.brar@samsung.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/max77686.c

@@ -146,7 +146,7 @@ static int max77686_ldo_set_suspend_mode(struct regulator_dev *rdev,
 				  val);
 }
 
-int max77686_enable(struct regulator_dev *rdev)
+static int max77686_enable(struct regulator_dev *rdev)
 {
 	struct max77686_data *max77686 = rdev_get_drvdata(rdev);