ASoC: soc-acpi: add helper to identify parent driver.

Intel machine drivers are used by parent platform drivers based on
closed-source firmware (Atom/SST and catpt) and SOF-based ones.

In some cases for ACPI-based platforms, the behavior of machine
drivers needs to be modified depending on the parent type, typically
for card names and power management.

An initial solution based on passing a boolean flag as a platform
device parameter was tested earlier. Since it looked overkill, this
patch suggests instead a simple string comparison to identify an SOF
parent device/driver.
Suggested-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@linux.intel.com>
Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Link: https://lore.kernel.org/r/20201112223825.39765-5-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

include/sound/soc-acpi.h

@@ -171,4 +171,10 @@ struct snd_soc_acpi_codecs {
 	u8 codecs[SND_SOC_ACPI_MAX_CODECS][ACPI_ID_LEN];
 };
 
+static inline bool snd_soc_acpi_sof_parent(struct device *dev)
+{
+	return dev->parent && dev->parent->driver && dev->parent->driver->name &&
+		!strcmp(dev->parent->driver->name, "sof-audio-acpi");
+}
+
 #endif