net: ethernet: mtk-star-emac: modify IRQ trigger flags

If the flags in request_irq() is IRQF_TRIGGER_NONE, the trigger method
is determined by "interrupt" property in dts.
So, modify the flag from IRQF_TRIGGER_FALLING to IRQF_TRIGGER_NONE.

Signed-off-by: Biao Huang <biao.huang@mediatek.com>
Signed-off-by: Yinghua Pan <ot_yinghua.pan@mediatek.com>
Reviewed-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>