ASoC: Intel: Skylake: Update FW purge for Broxton

Broxton needs to send Purge firmware IPC to DSP before downloading the
firmware. The DMA id needs to be updated for that.

While at it also update Broxton boot sequence to send purge request after
power up and before yanking off reset.

Signed-off-by: Senthilnathan Veppur <senthilnathanx.veppur@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>