gpio: mpc8xxx: Add wake on GPIO support

gpio: mpc8xxx: Add wake on GPIO support

The mpc8xxx GPIO can generate an interrupt on state change. This
interrupt can be used to wake up the device from its sleep state if
enabled to do so. Add required support to the driver so that the GPIO
can be used in this way.

In order for the GPIO to actually function in this way, it is necessary
to also set the GPIO bit in the RCPM. This can be done via the device
tree fsl,rcpm-wakeup property.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>
Link: https://lore.kernel.org/r/20240820143328.1987442-1-martyn.welch@collabora.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>