rtc: ingenic: Enable clock in probe

It makes no sense to request a clock and not enable it even though the
hardware is being used. So the driver now enables the clock in the
probe. Besides, now we can properly handle errors.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20200505221336.222313-3-paul@crapouillou.net


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>