OMAP3: PM: PRCM interrupt: only handle selected PRCM interrupts

Clearing wakeup sources is now only done when the PRM indicates a
wakeup source interrupt.  Since we don't handle any other types of
PRCM interrupts right now, warn if we get any other type of PRCM
interrupt.  Either code needs to be added to the PRCM interrupt
handler to react to these, or these other interrupts should be masked
off at init.

Updated after Jon Hunter's PRCM IRQ rework by Kevin Hilman.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>