ASoC: fsl: imx-card: initialize playback_only and capture_only

ASoC: fsl: imx-card: initialize playback_only and capture_only

Fix uninitialized variable playback_only and capture_only because
graph_util_parse_link_direction() may not write them.

Fixes: 1877c3e7937f ("ASoC: imx-card: Add playback_only or capture_only support")
Suggested-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Link: https://patch.msgid.link/20260318102850.2794029-3-shengjiu.wang@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>