ARM: dts: imx6: RDU2: enable RMI4 reduced reporting

To use the reduced reporting mode the threshold values need to be set
explicitly. Configure the threshold to be less than 0.5% of the full
touchscreen range. This seems to be a good compromise between system
load and input accurancy.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>