ASoC: wm0010.c: add static to local variable

Also add const to array

 text	   data	    bss	    dec	    hex	filename
 10946	   2904	   3528	  17378	   43e2	sound/soc/codecs/wm0010.o-before
 10891	   2840	   3512	  17243	   435b	sound/soc/codecs/wm0010.o-after

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Mark Brown <broonie@linaro.org>