ARM: dts: at91: sama5d2: remove atmel,wakeup-type references

atmel,wakeup-type DT property is not referenced anywhere in the current
and previous version of the code thus remove it.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Nicolas Ferre <nferre@kernel.org>
Link: https://lore.kernel.org/r/1609845525-10766-1-git-send-email-claudiu.beznea@microchip.com