iio: fix position relative kernel version

Position relative channel type was added in 4.19 kernel version

Fixes: "3055a6cfa04ba" ("iio: Add channel for Position Relative")
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
1 file changed