iio: stmpe-adc: Reinit completion struct on begin conversion

In some cases, the wait_completion got interrupted. This caused the
error-handling to mutex_unlock the function. The before turned on
interrupt then got called anyway. In the ISR then completion() was
called causing wrong adc-values returned in a following adc-readout.

Reinitialise completion struct to make sure the counter is zero
when beginning a new adc-conversion.
Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/stmpe-adc.c

@@ -65,6 +65,8 @@ static int stmpe_read_voltage(struct stmpe_adc *info,
 
 	mutex_lock(&info->lock);
 
+	reinit_completion(&info->completion);
+
 	info->channel = (u8)chan->channel;
 
 	if (info->channel > STMPE_ADC_LAST_NR) {
@@ -103,6 +105,8 @@ static int stmpe_read_temp(struct stmpe_adc *info,
 
 	mutex_lock(&info->lock);
 
+	reinit_completion(&info->completion);
+
 	info->channel = (u8)chan->channel;
 
 	if (info->channel != STMPE_TEMP_CHANNEL) {