ASoC: fsl_audmix: register card device depends on 'dais' property

ASoC: fsl_audmix: register card device depends on 'dais' property

[ Upstream commit 294a60e5e9830045c161181286d44ce669f88833 ]

In order to make the audmix device linked by audio graph card, make
'dais' property to be optional.

If 'dais' property exists, then register the imx-audmix card driver.
otherwise, it should be linked by audio graph card.

Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Link: https://patch.msgid.link/20250226100508.2352568-5-shengjiu.wang@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>