ASoC: pcm512x: Add regmap select

We need at least the core regmap code to build.

Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/sound/soc/codecs/Kconfig b/sound/soc/codecs/Kconfig
index 56d0c28..fa47a83 100644
--- a/sound/soc/codecs/Kconfig
+++ b/sound/soc/codecs/Kconfig
@@ -316,6 +316,7 @@
 
 config SND_SOC_PCM512x
        tristate "Texas Instruments PCM512x CODECs"
+       select REGMAP
 
 config SND_SOC_RT5631
 	tristate