gpio/omap: fix wakeup_en register update in _set_gpio_wakeup()
There are two ways through which wakeup_en register can be programmed
using gpiolib APIs as shown below. It is seen that in the second case
in _set_gpio_wakeup(), even though bank->suspend_wakeup is updated
correctly, its value is not programmed in wakeup_en register. Fix this.