ARM: dts: at91: ge863-pro3: use TCB0 as timers

Use tcb0 for timers as selected in at91_dt_defconfig.

Cc: Fabio Porcedda <fabio.porcedda@gmail.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>