plat-nomadik: support secondary GPIO interrupts

When GPIOs wake up the system from sleep mode, the normal GPIO interrupt
handler does not hit and the normal interrupt status register does not
contain the status. Instead the secondary GPIO handler does, and the
interrupt status needs to be retrieved from the wakeup status saved by
the suspend/resume code.

Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>