ASoC: SMDK_WM8580: Make I2S0 as default dai

Since most newer SMDKs have I2S0 routed to the WM8580's Primary DAI,
future changes can be minimized if the default CPU DAIs are set to
0, rather than 2.

Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>