irqchip/ingenic: Leave parent IRQ unmasked on suspend

All the wakeup sources we possibly want will go through the interrupt
controller, so the parent IRQ must not be masked during suspend, or
there won't be any way to wake up the system.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200819180602.136969-1-paul@crapouillou.net