rtc: pl031: set range

The PL031 and ST v1 RTC are 32bit seconds counters. STv2 is a BCD RTC
apparently going from 0000 to 9999, hopefully handling the leap days
properly until then.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20200306005809.38530-2-alexandre.belloni@bootlin.com


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