Add I2C driver for Summit Microelectronics SMB347 Battery Charger.

Driver support for the Summit I²C battery charger. This is used in some
Intel devices.

Signed-off-by: Bruce E. Robertson <bruce.e.robertson@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>