iio: potentiometer: mcp4018: use the correct MODULE_LICENSE

The file is GPL v2 only.

Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Peter Rosin 2018-08-20 12:01:10 +02:00 • committed by Jonathan Cameron
commit b9ea8c31e3