rtc: s3c: Remove dead code related to periodic tick handling

Support for periodic tick interrupts has been moved from the RTC class to
the HR-timers long time ago. Then it has been removed from this driver by
commits 80d4bb51 ("RTC: Cleanup rtc_class_ops->irq_set_state") and
696160fe ("RTC: Cleanup rtc_class_ops->irq_set_freq()"). They however
did not remove all the code related to the tick handling. Do it now then.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201202111318.5353-2-m.szyprowski@samsung.com