ASoC: lm4857: Use SOC_ENUM_SINGLE_EXT_DECL()

Just replace with the helper macro.  No functional change at all.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/codecs/lm4857.c

@@ -101,8 +101,7 @@ static const char *lm4857_mode[] = {
 	"Headphone",
 };
 
-static const struct soc_enum lm4857_mode_enum =
-	SOC_ENUM_SINGLE_EXT(ARRAY_SIZE(lm4857_mode), lm4857_mode);
+static SOC_ENUM_SINGLE_EXT_DECL(lm4857_mode_enum, lm4857_mode);
 
 static const struct snd_soc_dapm_widget lm4857_dapm_widgets[] = {
 	SND_SOC_DAPM_INPUT("IN"),