Input: edt-ft5x06 - remove support for platform data

We do not have any users of platform data in the tree and all newer
platforms are either DT or ACPI, so let's drop handling of platform data.

Tested-by: Franklin S Cooper Jr <fcooper@ti.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>