leds: an30259a: add initial driver

There are five features supported in this driver.
You can specify each individual color with different settings or use one
setting applying to all of them. Here are the 5 features.
1. set maximum current setting to the chip
2. turn on led with certain brightness.
3. turn off led.
4. set pulse lighting mode with specific brightness value, and the time period
for on and off state.
5. set slope lighting mode, which led gradually lights on from brightness 0 to
mid_brightness, then from mid_brightness to full brightness. Then staying at
full brightness for a certain period of time; then dim from full brightness to
mid_brightness, from mid_brightness to 0, and then staying for a certain time.

Change-Id: I6c567b41fb400e3ba199d50f194f7257caa5b4e5
Signed-off-by: Yufi Li <tyli@sta.samsung.com>
Signed-off-by: Won Hyoung Lee <whlee@sta.samsung.com>

Conflicts:
	drivers/misc/Makefile