backlight: add Backlight driver for lm3630 chip

This driver is a general version for LM3630 backlgiht driver chip of TI.

LM3630 :
The LM3630 is a current mode boost converter which supplies the power
and controls the current in two strings of up to 10 LEDs per string.
Programming is done over an I2C compatible interface.
www.ti.com

[akpm@linux-foundation.org: make bled_name[] static, a few coding style tuneups, create new set_intensity(), partly to avoid awkward layout gymnastics]
Signed-off-by: G.Shark Jeong <gshark.jeong@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Daniel Jeong <daniel.jeong@ti.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>