ASoC: Remove needless codec->bias_level assignment to SND_SOC_BIAS_OFF

This assignment is done by the snd_soc_register_codec so there is no need
to redo it in probe function of a codec driver.

Signed-off-by: Jarkko Nikula <jhnikula@gmail.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>