ASoC: SOF: Add driver debug support.

Add debugFS files that can be used to expose DSP memories and
and peripherals to userspace to assist with firmware debugging.

Since we cannot rely on debugFS, errors are logged but don't stop
execution.

When a resource cannot be read in D3, it is optionally cached on
suspend. Copying memories from IO will increase the suspend latency,
this should only used in engineering builds w/ debug options. This
part will have to be enhanced when support for D0ix states is
provided, currently only D0 and D3 are supported.

Signed-off-by: Pan Xiuli <xiuli.pan@linux.intel.com>
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
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>