irqchip/irq-bcm7038-l1: Add PM support

The current L1 controller does not mask any interrupts when dropping
into suspend. This mean we can receive unexpected wake up sources.
Modified the BCM7038 L1 controller to mask the all non-wake interrupts
before dropping into suspend.

Signed-off-by: Justin Chen <justinpopo6@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20191024201415.23454-2-f.fainelli@gmail.com