ASoC: Intel: Skylake: add DSP platform widget event handlers

The Skylake driver topology model tries to model the firmware
rule for pipeline and module creation.
The creation rule is:
 - Create Pipe
 - Add modules to Pipe
 - Connect the modules (bind)
 - Start the pipes

Similarly destroy rule is:
 - Stop the pipe
 - Disconnect it (unbind)
 - Delete the pipe

In driver we use Mixer, as there will always be ONE mixer in a
pipeline to model a pipe. The modules in pipe are modelled as PGA
widgets.  The DAPM sequencing rules (mixer and then PGA) are used
to create the sequence DSP expects as depicted above, and then
widget handlers for PMU and PMD events help in that.

This patch adds widget event handlers for PRE/POST PMU and
PRE/POST PMD event for mixer and pga modules.  These event
handlers invoke pipeline creation, destroy, module creation,
module bind, unbind and pipeline bind unbind

Event handler sequencing is implement to target the DSP FW
sequence expectations to enable path from source to sink pipe for
Playback/Capture.

Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Signed-off-by: Hardik T Shah <hardik.t.shah@intel.com>
Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>