ASoC: move ACPI common code out of Intel/sst tree

ACPI support is not specific to the Intel/SST driver. Move the enumeration
and matching code which is not hardware-dependent to sound/soc and rename
relevant sst_acpi_ structures and functions with snd_soc_acpi_ prefix

soc-acpi.h is protected by a #ifndef __LINUX_SND_SOC_ACPI_H for
consistency with all other SoC .h files:

grep -L __LINUX include/sound/soc* | wc -l
0
grep __LINUX include/sound/soc* | wc -l
14

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