regulator: Enable supply regulator if child rail is enabled.

During regulator_register, the rail is set on the provided
machine constraints and if it is enabled then it is also
require to enable the supply regulator. This will make sure
that:
   1. Proper reference count for supply regulator to be maintain.
   2. Supply regulator should be enable when given rail is enabled.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/core.c

@@ -2802,6 +2802,14 @@ struct regulator_dev *regulator_register(struct regulator_desc *regulator_desc,
 		ret = set_supply(rdev, r);
 		if (ret < 0)
 			goto scrub;
+
+		/* Enable supply if rail is enabled */
+		if (rdev->desc->ops->is_enabled &&
+				rdev->desc->ops->is_enabled(rdev)) {
+			ret = regulator_enable(rdev->supply);
+			if (ret < 0)
+				goto scrub;
+		}
 	}
 
 	/* add consumers devices */