ARM: dts: at91-sama5d4: use IRQ_TYPE_* to specify irq flags

According to the binding documentation and the source code the atmel-gpio
controller takes IRQ_TYPE_* as its flags values, not GPIO_ACTIVE_*.

This patch uses the right variable type which yields the same result
when compiled. Note that this might be wrong and actually
IRQ_TYPE_LEVEL_LOW is intended by the dt author.

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Acked-by: Marek Vasut <marex@denx.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>