This driver is a general version for LM642 led chip of TI.

LM3642 :
The LM3642 is a 4MHz fixed-frequency synchronous boost
converter plus 1.5A constant current driver for a high-current
white LED.
The LM3642 is controlled via an I2C-compatible interface.
Signed-off-by: NG.Shark Jeong <gshark.jeong@gmail.com>
Signed-off-by: NBryan Wu <bryan.wu@canonical.com>