rtc: da9063: add as wakeup source

As da9063 RTC is not a real I2C client, but relies on da9063 MFD
driver, we need to explicitly mark da9063 RTC as a wakeup source
to be able to access class/rtc/rtcN/wakealarm sysfs entry
to set alarms, so we can wakeup from SHUTDOWN/RTC/DELIVERY mode.

As da9063 driver refuses to load without irq, we simply add it
as a wakeup source before registering rtc device.

Signed-off-by: Nikita Shubin <nikita.shubin@maquefel.me>
Reviewed-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20211129072650.22686-1-nikita.shubin@maquefel.me