ASoC: simple_card_utils: fix fallback when "label" property isn't present

ASoC: simple_card_utils: fix fallback when "label" property isn't present

snd_soc_of_parse_card_name() doesn't return an error if the requested
property isn't present, but silently fails to fill the card name. This can
not be changed, as it is a backwards compatibility measure itself.

We can not rely on the return value of this function alone, but must check
if the card name has been filled sucessfully when deciding to skip the
fallback path, which is in place for existing users.

Fixes: dedfaa1eedc7 (ASoC: simple-card-utils: enable "label" on
                     asoc_simple_card_parse_card_name)
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>