ASoC: wm_adsp: Ensure set controls are synced on each boot

Rename `dirty' to `set' as it is a bit more descriptive.  A set
control is any control that has been set by the user.  We need to ensure
that everytime we boot the DSP we sync out any controls that were
set.

We could at some point start keeping track of the default values of
the controls to suppress some of the device I/O.

Signed-off-by: Dimitris Papastamos <dp@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>