ASoC: rl6231: make arrays div and pd static const, reduces object code size

Don't populate the read-only arrays div and pd on the stack,
instead make them static const. Makes the object code smaller by 210 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
   2869	    720	      0	   3589	    e05	sound/soc/codecs/rl6231.o

After:
   text	   data	    bss	    dec	    hex	filename
   2495	    880	      0	   3375	    d2f	sound/soc/codecs/rl6231.o

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Mark Brown <broonie@kernel.org>