ASoC: zx-i2s: flip I2S master/slave mode

The SND_SOC_DAIFMT_MASTER bits are defined to specify the master/slave
mode for Codec, not I2S.  So the I2S master/slave mode should be flipped
according to SND_SOC_DAIFMT_MASTER bits.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org