OMAP: GPIO: Avoid generating extra IRQs

It is possible for GPIO IRQ lines configured with
falling edge triggering only to get IRQs at the
rising edge upon the exit of offmode. And vice
versa. Prevent such IRQs to arrive by generating
the IRQ obeying the detection scheme.

Signed-off-by: Eero Nurkkala <ext-eero.nurkkala@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>