leds: lp8501: make several arrays static const

Don't populate the arrays on the stack, instead make them static const.
Makes the object code smaller by 50 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
   5058	   1552	     64	   6674	   1a12	drivers/leds/leds-lp8501.o

After:
   text	   data	    bss	    dec	    hex	filename
   4788	   1776	     64	   6628	   19e4	drivers/leds/leds-lp8501.o

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>