ARM: dts: imx51-zii-rdu1: fix touchscreen bindings

This fixes errors in RDU1 device tree that cause touch screens not
working.

Fixes: ceef0396

 ("ARM: dts: imx: add ZII RDU1 board")
Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>