leds: add BD2802GU LED driver

ROHM BD2802GU is a RGB LED controller attached to i2c bus and specifically
engineered for decoration purposes.  This RGB controller incorporates
lighting patterns and illuminates.

This driver is designed to minimize power consumption, so when there is no
emitting LED, it enters to reset state.  And because the BD2802GU has lots
of features that can't be covered by the current LED framework, it
provides Advanced Configuration Function(ADF) mode, so that user
applications can set registers of BD2802GU directly.

Here are basic usage examples :
; to turn on LED (not blink)
$ echo 1 > /sys/class/leds/led1_R/brightness
; to blink LED
$ echo timer > /sys/class/leds/led1_R/trigger
$ echo 1 > /sys/class/leds/led1_R/delay_on
$ echo 1 > /sys/class/leds/led1_R/delay_off
; to turn off LED
$ echo 0 > /sys/class/leds/led1_R/brightness

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Kim Kyuwon <chammoru@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>