hwmon: (ads1015) Add support for ADS1115

This patch adds support for ads1115 device to ads1015 driver.
Based on work of Emiliano Carnati <carnatiatebneuro.com>.
Tested on ARM CPU based board.

Signed-off-by: Evgeniy A. Dushistov <dushistov@mail.ru>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>