iio: temperature: ltc2983: Fix reinit_completion() called after conversion start

reinit_completion() was called after regmap_write() initiated the hardware
conversion, creating a race window where the interrupt could fire and call
complete() before reinit_completion() reset the completion.

Move reinit_completion() before the regmap_write() to close the race.
ltc2983_eeprom_cmd() already does it in the correct order.

Fixes: f110f31 ("iio: temperature: Add support for LTC2983")
Signed-off-by: Liviu Stan <liviu.stan@analog.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

Author: leaveyoustun

drivers/iio/temperature/ltc2983.c

@@ -1177,12 +1177,11 @@ static int ltc2983_chan_read(struct ltc2983_data *st,
 	start_conversion |= LTC2983_STATUS_CHAN_SEL(sensor->chan);
 	dev_dbg(&st->spi->dev, "Start conversion on chan:%d, status:%02X\n",
 		sensor->chan, start_conversion);
+	reinit_completion(&st->completion);
 	/* start conversion */
 	ret = regmap_write(st->regmap, LTC2983_STATUS_REG, start_conversion);
 	if (ret)
 		return ret;
-
-	reinit_completion(&st->completion);
 	/*
 	 * wait for conversion to complete.
 	 * 300 ms should be more than enough to complete the conversion.