ASoC: SOF: Add Sound Open Firmware KControl support

SOF exposes regular ALSA Kcontrols that are defined by topology. This
patch converts the Kcontrol IO to DSP IPC.

The current implementation is aligned with previous Intel solutions,
but is not optimal and can be improved:
a) for every get/put the host wakes up the DSP and generates an
IPC. The kernel should cache the values and generate an IPC only when
strictly necessary.
b) the firmware can be implemented to only instantiate the pipelines
and related control-related parts that are needed at a given time, and
power-gate the relevant SRAM blocks.

The development tasks for these two improvements has started, once
validated they will be provided in an update.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>