ASoC: Route all bias level updates through the core

Use the new snd_soc_codec_force_bias_level() helper function to invoke the
bias_level callback of a driver instead of calling the callback by hand.
Currently the effect of this is the same, but having all bias level updates
go through a central place will allow us to move more of the bias level
management into the DAPM core.

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