ASoC: pcm512x: Add regmap select

We need at least the core regmap code to build.
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/codecs/Kconfig

@@ -316,6 +316,7 @@ config SND_SOC_PCM3008
 
 config SND_SOC_PCM512x
        tristate "Texas Instruments PCM512x CODECs"
+       select REGMAP
 
 config SND_SOC_RT5631
 	tristate