This fixes the following build errors when aic23 is configured as
module:

>> ERROR: "tlv320aic23_probe"
>> [sound/soc/codecs/snd-soc-tlv320aic23-i2c.ko] undefined!
>> ERROR: "tlv320aic23_regmap"
>> [sound/soc/codecs/snd-soc-tlv320aic23-i2c.ko] undefined!
Signed-off-by: NMax Filippov <jcmvbkbc@gmail.com>
Signed-off-by: NMark Brown <broonie@linaro.org>