ASoC: wm_adsp: Start DSP booting earlier in the DAPM process

Move the start of booting the DSP to earlier in the DAPM process, and
move the final starting of the DSP to later in the DAPM process. This
allows us to overlap some of the processing with other components of the
system being brought up.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@linaro.org>