rtc: spear: set range

While the RTC can store dates from year 0000 to 9999, leap years where not
tested fro 2100. The driver currently stores tm_year directly which will
probably fail at that time or more probably in 2300.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/20220309162301.61679-19-alexandre.belloni@bootlin.com