ASoC: mediatek: avoid using snd_soc_platform

avoid using snd_soc_platform, which is removed after 4.18
Signed-off-by: KaiChieh Chuang <kaichieh.chuang@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/mediatek/common/mtk-afe-platform-driver.c

@@ -62,7 +62,7 @@ static int mtk_afe_pcm_new(struct snd_soc_pcm_runtime *rtd)
 
 	size = afe->mtk_afe_hardware->buffer_bytes_max;
 	return snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV,
-						     rtd->platform->dev,
+						     afe->dev,
 						     size, size);
 }