ASoC: use seq_file to dump the contents of dai_list,platform_list and codec_list

Now the debugfs files dais/platforms/codecs have a size limit PAGE_SIZE and
the user can not see the whole contents of dai_list/platform_list/codec_list
when they are larger than this limit.

This patch uses seq_file instead to make sure dais/platforms/codecs show the
full contents of dai_list/platform_list/codec_list.

Signed-off-by: Donglin Peng <dolinux.peng@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>