iio: cros_ec_sensors_core: fix unsigned compared less than zero on status

status is a u8 hence the check if status is less than zero has no effect.
Fix this by replacing status with int ret so the less than zero compare
will correctly detect errors.

Issue found with static analysis with CoverityScan, CID 1375919

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Fixes: 974e6f02 ("iio: cros_ec_sensors_core: Add common functions for the ChromeOS EC Sensor Hub")
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>