gpio/omap4: Fix missing interrupts during device wakeup due to IOPAD.

If gpio pins from bank[2-5] are marked as wakeup enable and if the wake is
through gpio IO pad wakeup, then that wakeup gpio interrupt is lost.

In the current implementation, GPIO driver stores the context of DATAIN of
all the gpio in the bank. During GPIO resuming, it checks DATAIN with wakeup
enabled pins of gpio bank. If there is status change, then manually toggle
GPIO_LEVELDETECT to generate pseudo interrupt.

Reported-by: Philippe Mazet <p-mazet@ti.com>
Tested-by: Philippe Mazet <p-mazet@ti.com>
Signed-off-by: Ambresh K <ambresh@ti.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>