ASoC: sta32x: Move resource allocation and release to the corresponding callback functions

This patch includes below small fixes:

1. Move sta32x_set_bias_level() from sta32x_i2c_remove() to sta32x_remove().
2. Remove a redundant regulator_bulk_free() call in sta32x_i2c_remove(),
   as we will call regulator_bulk_free() in sta32x_remove().
3. Remove unneeded snd_soc_codec_set_drvdata(codec, NULL) in sta32x_i2c_remove.
   The i2c core will set the clientdata to NULL.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Johannes Stezenbach <js@sig21.net>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>