ASoC: fsl_sai: Fix incorrect condition check in trigger()

Patch ASoC: fsl_sai: Fix buggy configurations in trigger() doesn't entirely
fix the condition: FRDE of the current substream direction is being cleared
while the code is still using the non-updated one.

Thus this patch fixes this issue by checking the opposite one's FRDE alone
since the current one's is absolutely disabled.

Signed-off-by: Nicolin Chen <Guangyu.Chen@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>