ASoC: Remove snd_soc_update_bits_locked()

There are no users of snd_soc_update_bits_locked() left and it is identical to
snd_soc_update_bits(). So it can be removed.

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