ASoC: soc-core: fix DMI handling

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: c014170408bc ("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.com
Signed-off-by: Mark Brown <broonie@kernel.org>