I2C-controlled sensor measures ambient and object temperatuer

see
http://www.melexis.com/Infrared-Thermometer-Sensors/Infrared-Thermometer-Sensors/MLX90614-615.aspxSigned-off-by: NPeter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>