ASoC: soc-core: fix DMI handling

When DMI information is not present, trying to assign the card long
name results in the following warning.

WARNING KERN tegra-audio-graph-card sound: ASoC: no DMI vendor name!

The initial solution suggested was to test if the card device is an
ACPI one. This causes a regression visible to userspace on all Intel
platforms, with UCM unable to load card profiles based on DMI
information: the card devices are not necessarily ACPI ones, e.g. when
the parent creates platform devices on Intel devices.

To fix this problem, this patch exports the existing dmi_available
variable and tests it in the ASoC core.

Fixes: c0141704 ("ASoC: soc-core: Prevent warning if no DMI table is present")
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Jean Delvare <jdelvare@suse.de>
Link: https://lore.kernel.org/r/20210310193928.108850-1-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/firmware/dmi_scan.c

@@ -166,6 +166,7 @@ static int __init dmi_checksum(const u8 *buf, u8 len)
 static const char *dmi_ident[DMI_STRING_MAX];
 static LIST_HEAD(dmi_devices);
 int dmi_available;
+EXPORT_SYMBOL_GPL(dmi_available);
 
 /*
  *	Save a DMI string

sound/soc/soc-core.c

@@ -1574,7 +1574,7 @@ int snd_soc_set_dmi_name(struct snd_soc_card *card, const char *flavour)
 	if (card->long_name)
 		return 0; /* long name already set by driver or from DMI */
 
-	if (!is_acpi_device_node(card->dev->fwnode))
+	if (!dmi_available)
 		return 0;
 
 	/* make up dmi long name as: vendor-product-version-board */