ASoC: hdac_hda: add asoc extension for legacy HDA codec drivers

This patch adds a kernel module which is used by the legacy HDA
codec drivers as library. This implements hdac_ext_bus_ops to enable
the reuse of legacy HDA codec drivers with ASoC platform drivers.

Signed-off-by: Rakesh Ughreja <rakesh.a.ughreja@intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/intel/boards/Kconfig

@@ -283,6 +283,7 @@ config SND_SOC_INTEL_KBL_DA7219_MAX98357A_MACH
 config SND_SOC_INTEL_SKL_HDA_DSP_GENERIC_MACH
 	tristate "SKL/KBL/BXT/APL with HDA Codecs"
 	select SND_SOC_HDAC_HDMI
+	select SND_SOC_HDAC_HDA
 	help
 	  This adds support for ASoC machine driver for Intel platforms
 	  SKL/KBL/BXT/APL with iDisp, HDA audio codecs.