drivers: iio: cdc: Drop redundant if check

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alexander Vorwerk <zabe@avorwerk.net>
Link: https://lore.kernel.org/r/20230105025351.12099-1-zabe@avorwerk.net


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