rtc: hym8563: enable wakeup when applicable

Enable wakeup in the hym8563 driver if the IRQ was successfully
requested or if wakeup-source is set in the devicetree.

As per the description of device_init_wakeup(), it should be enabled
for "devices that everyone expects to be wakeup sources".  One would
expect this to be the case with a real-time clock.

Tested on rk3288-rock2-square, which has an IRQ configured for the
RTC.  As a result, wakeup was enabled during driver initialisation.

Fixes: dcaf0384 ("rtc: add hym8563 rtc-driver")
Reported-by: kernelci.org bot <bot@kernelci.org>
Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/1ea023e2ba50a4dab6e39be93d7de3146af71a60.1604653374.git.guillaume.tucker@collabora.com