ARM: dts: at91-sama5d2_xplained: Use IRQ_TYPE specifier

GPIO_ACTIVE_LOW was being used to specify an interrupt, use
IRQ_TYPE_EDGE_RISING instead. This improves DT readability.

Signed-off-by: Hernán Gonzalez <hernan@vanguardiasur.com.ar>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>