leds: aat1290: make array max_mm_current_percent static const

Don't populate the array max_mm_current_percent on the stack, instead
make it static const.  Makes the object code smaller by over 280 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
   7225	   1936	     64	   9225	   2409	./drivers/leds/leds-aat1290.o

After:
   text	   data	    bss	    dec	    hex	filename
   6847	   2032	     64	   8943	   22ef	./drivers/leds/leds-aat1290.o`

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