OMAP: Add new function to check wether there is irq pending

Add common omap2/3 function to check wether there is irq pending.
Switch to use it in omap2 pm code instead of its own.

Signed-off-by: Jouni Hogander <jouni.hogander@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>