MAINTAINERS: add co-maintainer for LED subsystem

Add myself (Jacek Anaszewski) as a co-maintainer for the LED subsystem.

Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Acked-by: Bryan Wu <cooloney@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>