Input: edt-ft5x06 - drop parsing of irq gpio

The driver does not use irq gpio as gpio, but rather relies on I2C core or
board code to set up client's structure IRQ line, so let's stop trying to
locate the resource and parse it.

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