power: supply: Add driver for Microchip UCS1002

Add driver for Microchip UCS1002 Programmable USB Port Power
Controller with Charger Emulation. The driver exposed a power supply
device to control/monitor various parameter of the device as well as a
regulator to allow controlling VBUS line.

Signed-off-by: Enric Balletbo Serra <enric.balletbo@collabora.com>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: linux-kernel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>