ASoC: fsl_ssi: Add DAIFMT define for AC97

The _fsl_ssi_set_dai_fmt() bypasses an undefined format for AC97
mode. However, it's not really necessary if AC97 has its complete
format defined.

So this patch adds a DAIFMT macro of complete format including a
clock direction and polarity.

Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
Tested-by: Caleb Crome <caleb@crome.org>
Tested-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Reviewed-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Mark Brown <broonie@kernel.org>