Input: edt-ft5x06: Poll the device if no interrupt is configured.

Not all systems have the interrupt line wired up, so switch to
polling the touchscreen off a timer if no interrupt line is
configured.

Link: https://github.com/raspberrypi/linux/commit/ca61fdaba79fa29fc950b3b731c99557d6781ff5



Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Rahul T R <r-ravikumar@ti.com>