ASoC: mt6351: remove unused variable 'mt_lineout_control'

sound/soc/codecs/mt6351.c:1070:38: warning:
 mt_lineout_control defined but not used [-Wunused-const-variable=]

It is never used, so can be removed.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20190809080234.23332-1-yuehaibing@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/mt6351.c

@@ -1066,11 +1066,6 @@ static int mt_mic_bias_2_event(struct snd_soc_dapm_widget *w,
 	return 0;
 }
 
-/* DAPM Kcontrols */
-static const struct snd_kcontrol_new mt_lineout_control =
-	SOC_DAPM_SINGLE("Switch", MT6351_AUDDEC_ANA_CON3,
-			RG_AUDLOLPWRUP_VAUDP32_BIT, 1, 0);
-
 /* DAPM Widgets */
 static const struct snd_soc_dapm_widget mt6351_dapm_widgets[] = {
 	/* Digital Clock */