regulator: Defer lookup of supply to regulator_get

Instead of resolving regulator supplies during registration move this to
the time of a consumer retrieving a handle. The benefit is that it's
possible for one driver to register regulators with internal
dependencies out of order.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

include/linux/regulator/driver.h

@@ -367,6 +367,7 @@ struct regulator_dev {
 	struct device dev;
 	struct regulation_constraints *constraints;
 	struct regulator *supply;	/* for tree */
+	const char *supply_name;
 	struct regmap *regmap;
 
 	struct delayed_work disable_work;