ASoC: fsl-asoc-card: constify fsl_asoc_card_dai

This is never modified and can be made const.

Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Link: https://lore.kernel.org/r/20230126152412.959574-1-luca.ceresoli@bootlin.com


Signed-off-by: Mark Brown <broonie@kernel.org>