ASoC: wm8988: Constify struct regmap_config and snd_soc_codec_driver

The regmap_config struct may be const because it is not modified by the
driver and regmap_init() accepts pointer to const. Make struct
snd_soc_codec_driver const as well (snd_soc_register_codec() accepts
pointer to const).
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: Brian Austin <brian.austin@cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/wm8988.c

@@ -813,7 +813,7 @@ static int wm8988_probe(struct snd_soc_codec *codec)
 	return 0;
 }
 
-static struct snd_soc_codec_driver soc_codec_dev_wm8988 = {
+static const struct snd_soc_codec_driver soc_codec_dev_wm8988 = {
 	.probe =	wm8988_probe,
 	.set_bias_level = wm8988_set_bias_level,
 	.suspend_bias_off = true,
@@ -826,7 +826,7 @@ static struct snd_soc_codec_driver soc_codec_dev_wm8988 = {
 	.num_dapm_routes = ARRAY_SIZE(wm8988_dapm_routes),
 };
 
-static struct regmap_config wm8988_regmap = {
+static const struct regmap_config wm8988_regmap = {
 	.reg_bits = 7,
 	.val_bits = 9,