ASoC: core: Don't set "(null)" as a driver name

Commit 22de71ba ("ASoC: core - allow ASoC more flexible machine name")
writes "(null)" to driver name string in struct snd_card if card->driver_name
is NULL. This causes segmentation faults with some user space ALSA utilities
like aplay and arecord.

Fix this by using the card->name if no driver name is specified.
Signed-off-by: Jarkko Nikula <jhnikula@gmail.com>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/soc-core.c

@@ -1930,7 +1930,7 @@ static void snd_soc_instantiate_card(struct snd_soc_card *card)
 	snprintf(card->snd_card->longname, sizeof(card->snd_card->longname),
 		 "%s", card->long_name ? card->long_name : card->name);
 	snprintf(card->snd_card->driver, sizeof(card->snd_card->driver),
-		 "%s", card->driver_name);
+		 "%s", card->driver_name ? card->driver_name : card->name);
 
 	if (card->late_probe) {
 		ret = card->late_probe(card);