ASoC: tlv320aic26: Fix keyclick feature

The tlv320aic26 contains a embedded snd_soc_codec struct which is referenced in
the keyclick code. That struct is never initialized though, replace the embedded
struct with a pointer and use that in the keyclick code.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>