ASoC: wm8900: remove some defined but not used symbols

Fix the following gcc warning:

sound/soc/codecs/wm8900.c:449:38: warning:
‘wm8900_dapm_routput2_control’ defined but not used
[-Wunused-const-variable=]
 static const struct snd_kcontrol_new wm8900_dapm_routput2_control =
                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
sound/soc/codecs/wm8900.c:446:38: warning:
‘wm8900_dapm_loutput2_control’ defined but not used
[-Wunused-const-variable=]
 static const struct snd_kcontrol_new wm8900_dapm_loutput2_control =
                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Link: https://lore.kernel.org/r/20200407082932.41511-5-yanaijie@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/wm8900.c

@@ -443,12 +443,6 @@ SOC_SINGLE("LINEOUT2 LP -12dB", WM8900_REG_LOUTMIXCTL1,
 
 };
 
-static const struct snd_kcontrol_new wm8900_dapm_loutput2_control =
-SOC_DAPM_SINGLE("LINEOUT2L Switch", WM8900_REG_POWER3, 6, 1, 0);
-
-static const struct snd_kcontrol_new wm8900_dapm_routput2_control =
-SOC_DAPM_SINGLE("LINEOUT2R Switch", WM8900_REG_POWER3, 5, 1, 0);
-
 static const struct snd_kcontrol_new wm8900_loutmix_controls[] = {
 SOC_DAPM_SINGLE("LINPUT3 Bypass Switch", WM8900_REG_LOUTMIXCTL1, 7, 1, 0),
 SOC_DAPM_SINGLE("AUX Bypass Switch", WM8900_REG_AUXOUT_CTL, 7, 1, 0),