serial: mctrl_gpio: add a new API to enable / disable wake_irq

Add a new API to enable / disable wake_irq in order to enable gpio irqs as
wakeup irqs for the uart port.

Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Link: https://lore.kernel.org/r/20220203171644.12231-2-erwan.leray@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>