IRQCHIP: brcmstb-l2: don't clear wakeable interrupts at init time
Wakeable interrupts might be pending at boot/init time, because wakeup
interrupts might have triggered a resume from S5. So don't clear such
wakeups.
This means that any driver which requests a wakeable interrupt bit
should be prepared to handle an interrupt as soon as they call
request_irq(). (This is technically already the correct development
practice, but some drivers probably expect not to receive interrupts
until they have performed some I/O.)