AT91: add touchscreen support for at91sam9g45ekes

New at91sam9g45ekes board provides a LCD with resistive touchscreen.
This is the support of this feature by atmel_tsadcc driver. This also
sets up platform parameters to be passed to the driver.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>