ARM: dts: imx6q-icore: Add touchscreen node

max11801 touchscreen on Engicam iCoreM6 Quad module is
connected via i2c1, so add max11801: touchscreen@48 on i2c1.

Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Domenico Acri <domenico.acri@engicam.com>
Cc: Matteo Lisi <matteo.lisi@engicam.com>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>