rtc: rtctest: add check for problematic dates

Some dates could be problematic because they reach the limits of
RTC hardware capabilities.
This patch add various of them but since it will change RTC date
it will be activated only when 'd' args is set.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>