ASoC: stm32: i2s: skip useless write in slave mode

Dummy write in capture master mode is used to gate
bus clocks. This write is useless in slave mode
as the clocks are not managed by slave.
Signed-off-by: NOlivier Moysan <olivier.moysan@st.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

sound/soc/stm/stm32_i2s.c

@@ -623,8 +623,8 @@ static int stm32_i2s_trigger(struct snd_pcm_substream *substream, int cmd,
 		} else {
 			ier = I2S_IER_OVRIE;
 
-			if (i2s->refcount == 1)
-				/* dummy write to trigger capture */
+			if (STM32_I2S_IS_MASTER(i2s) && i2s->refcount == 1)
+				/* dummy write to gate bus clocks */
 				regmap_write(i2s->regmap,
 					     STM32_I2S_TXDR_REG, 0);
 		}