Input: ili210x - do not set parent device explicitly

We are using devm_input_allocate_device() that set's up the parent for
us, no need to do it ourselves.

Tested-by: Adam Ford <aford173@gmail.com> #imx6q-logicpd
Tested-by: Sven Van Asbroeck <TheSven73@gmail.com> # ILI2118A variant
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>