ASoC: simple-card: is_top_level_node parameter to simple_card_dai_link_of()

Restore correct parsing of dai-link subnodes with more explicit
implementation for applying the "simple-audio-card,"-prefix to
dai-link property and subnode names.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>