ARM: mediatek: Add sysirq in mt6589/mt8135/mt8127 dtsi

Add sysirq settings for mt6589/mt8135/mt8127
This also correct timer interrupt flag. The old setting works
because boot loader already set polarity for timer interrupt.
Without intpol support, the setting was not changed so gic
can get the irq correctly.

Signed-off-by: Yingjoe Chen <yingjoe.chen@mediatek.com>
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>