ASoC: wm8991: remove defined but not used 'wm8991_dapm_rxvoice_controls'

Fix the following gcc warning:

sound/soc/codecs/wm8991.c:480:38: warning:
‘wm8991_dapm_rxvoice_controls’ defined but not used
[-Wunused-const-variable=]
 static const struct snd_kcontrol_new wm8991_dapm_rxvoice_controls[] = {
                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Link: https://lore.kernel.org/r/20200407082932.41511-3-yanaijie@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/wm8991.c

@@ -476,14 +476,6 @@ static SOC_ENUM_SINGLE_DECL(wm8991_ainrmux_enum,
 static const struct snd_kcontrol_new wm8991_dapm_ainrmux_controls =
 	SOC_DAPM_ENUM("Route", wm8991_ainrmux_enum);
 
-/* RXVOICE */
-static const struct snd_kcontrol_new wm8991_dapm_rxvoice_controls[] = {
-	SOC_DAPM_SINGLE_TLV("LIN4RXN", WM8991_INPUT_MIXER5, WM8991_LR4BVOL_SHIFT,
-		WM8991_LR4BVOL_MASK, 0, in_mix_tlv),
-	SOC_DAPM_SINGLE_TLV("RIN4RXP", WM8991_INPUT_MIXER6, WM8991_RL4BVOL_SHIFT,
-		WM8991_RL4BVOL_MASK, 0, in_mix_tlv),
-};
-
 /* LOMIX */
 static const struct snd_kcontrol_new wm8991_dapm_lomix_controls[] = {
 	SOC_DAPM_SINGLE("LOMIX Right ADC Bypass Switch", WM8991_OUTPUT_MIXER1,