ARM: at91/dt: ethernut5: use at91sam9xe.dtsi

The ethernut5 is actually based on an at91sam9xe, use the correct dts include.

Cc: Martin Reimann <martin.reimann@egnite.de>
Cc: Tim Schendekehl <tim.schendekehl@egnite.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>