iio: proximity: hx9023s: Fix error code in hx9023s_property_get()

If we're returning because "reg >= HX9023S_CH_NUM" then set the error code
to -ENIVAL instead of success.

Fixes: 60df5482 ("iio: proximity: Add driver support for TYHX's HX9023S capacitive proximity sensor")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://patch.msgid.link/49b5a9bc-e5ca-43a7-a665-313eb06fbe27@stanley.mountain


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>