iio: fix position relative kernel version

Position relative channel type was added in 4.19 kernel version

Fixes: "3055a6cf" ("iio: Add channel for Position Relative")
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/ABI/testing/sysfs-bus-iio

@@ -199,7 +199,7 @@ Description:
 
 What:		/sys/bus/iio/devices/iio:deviceX/in_positionrelative_x_raw
 What:		/sys/bus/iio/devices/iio:deviceX/in_positionrelative_y_raw
-KernelVersion:	4.18
+KernelVersion:	4.19
 Contact:	linux-iio@vger.kernel.org
 Description:
 		Relative position in direction x or y on a pad (may be