ASoC: core: Only add platform DAI widgets once.

Currently platform CPU DAI widgets are created in soc_probe_platform and
soc_probe_link_dais. Remove the extra call in soc_probe_link_dais().

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>