ASoC: Push snd_soc_write() and snd_soc_read() into the source file

Facilitating adding trace type stuff. For a first pass add some dev_dbg()
statements into them.

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