ASoC: Restore WM8994 volatile and readable register operations

They went AWOL during the multi-component merge.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: NLiam Girdwood <lrg@slimlogic.co.uk>

sound/soc/codecs/wm8994.c

@@ -4073,6 +4073,8 @@ static struct snd_soc_codec_driver soc_codec_dev_wm8994 = {
 	.resume =	wm8994_resume,
 	.read = wm8994_read,
 	.write = wm8994_write,
+	.readable_register = wm8994_readable,
+	.volatile_register = wm8994_volatile,
 	.set_bias_level = wm8994_set_bias_level,
 };