ASoC: wm8804: Remove superfluous const

As SOC_ENUM_SINGLE_DECL() itself contains const modifier now, we can
reduce const from its users.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/codecs/wm8804.c

@@ -92,7 +92,7 @@ WM8804_REGULATOR_EVENT(0)
 WM8804_REGULATOR_EVENT(1)
 
 static const char *txsrc_text[] = { "S/PDIF RX", "AIF" };
-static const SOC_ENUM_SINGLE_EXT_DECL(txsrc, txsrc_text);
+static SOC_ENUM_SINGLE_EXT_DECL(txsrc, txsrc_text);
 
 static const struct snd_kcontrol_new wm8804_snd_controls[] = {
 	SOC_ENUM_EXT("Input Source", txsrc, txsrc_get, txsrc_put),