ASoC: simple-card: Add snd_card's name parsing from DT node support

If the DT is used and the CPU DAI device has only one DAI, the card
name will be like :

ALSA device list:
0: 40031000.sai-sgtl5000

And this name maybe a little ugly to some customers, so here the
card name parsing from DT node is supported.

Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>