ASoC: ac97: Merge soc_ac97_dev_{un,}register()/soc_{un,}register_ac97_codec()

soc_{un,}register_ac97_codec() is just a simple wrapper around
soc_ac97_dev_{un,}register(). There is no need to split these up into two
different sets of functions.

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