ASoC: mmp-sspa: clear transmit phase bit for non-stereo formats

The transmit phase register value is never cleared during hw params.
So once hw params sets this bit to handle a two channel format, it
remains configured for dual-phase, which is not desirable for mono
playback.
Signed-off-by: Kyle Russell <bkylerussell@gmail.com>
Link: https://lore.kernel.org/r/20201106145905.365903-1-bkylerussell@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/pxa/mmp-sspa.c

@@ -239,6 +239,7 @@ static int mmp_sspa_hw_params(struct snd_pcm_substream *substream,
 		return -EINVAL;
 	}
 
+	sspa_ctrl &= ~SSPA_CTL_XPH;
 	if (dev->of_node || params_channels(params) == 2)
 		sspa_ctrl |= SSPA_CTL_XPH;