ASoC: don't use rtd->codec on fsl-asoc-card

rtd->codec will be removed soon.
rtd->codec = rtd->codec_dai->codec, thus,
we can use rtd->codec_dai->component instead of it.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>