iio:light:tsl2563: Replace cancel_delayed_work() with cancel_delayed_work_sync().

Since cancel_delayed_work(&chip->poweroff_work) does not guarantee that
tsl2563_poweroff_work() is not running, tsl2563_set_power(chip, 0) can be
called from tsl2563_poweroff_work() after tsl2563_get_power(chip) and
tsl2563_set_power(chip, 1) are called. Use _sync version in order to make
sure that tsl2563_poweroff_work() is no longer running.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Link: https://lore.kernel.org/r/041b6745-f784-ff3f-9836-3f4397d35d94@I-love.SAKURA.ne.jpSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/tsl2563.c

@@ -310,7 +310,7 @@ static int tsl2563_get_adc(struct tsl2563_chip *chip)
 		goto out;
 
 	if (!chip->int_enabled) {
-		cancel_delayed_work(&chip->poweroff_work);
+		cancel_delayed_work_sync(&chip->poweroff_work);
 
 		if (!tsl2563_get_power(chip)) {
 			ret = tsl2563_set_power(chip, 1);
@@ -638,7 +638,7 @@ static int tsl2563_write_interrupt_config(struct iio_dev *indio_dev,
 		chip->intr &= ~0x30;
 		chip->intr |= 0x10;
 		/* ensure the chip is actually on */
-		cancel_delayed_work(&chip->poweroff_work);
+		cancel_delayed_work_sync(&chip->poweroff_work);
 		if (!tsl2563_get_power(chip)) {
 			ret = tsl2563_set_power(chip, 1);
 			if (ret)