Since these macros are supposed to be used for decalring const
objects, let's add the const modifier there.

The doubled const appearing in usages will be cleaned by later
patches.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Acked-by: NLiam Girdwood <liam.r.girdwood@linux.intel.com>
Acked-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NMark Brown <broonie@linaro.org>