ASoC: rt5640: remove unused variable

We are getting build warning about:
sound/soc/codecs/rt5640.c:1892:11: warning: unused variable 'dai_sel'

The use of the variable was removed but the variable itself was not
removed.

Fixes: c467fc0e010b ("ASoC: rt5640: Set PLL src according to source")
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/rt5640.c

@@ -1889,7 +1889,7 @@ static int rt5640_set_dai_pll(struct snd_soc_dai *dai, int pll_id, int source,
 	struct snd_soc_codec *codec = dai->codec;
 	struct rt5640_priv *rt5640 = snd_soc_codec_get_drvdata(codec);
 	struct rl6231_pll_code pll_code;
-	int ret, dai_sel;
+	int ret;
 
 	if (source == rt5640->pll_src && freq_in == rt5640->pll_in &&
 	    freq_out == rt5640->pll_out)