rtc: Fix timestamp value for RTC_TIMESTAMP_BEGIN_1900

Printing "mktime64(1900, 1, 1, 0, 0, 0)" gives -2208988800.

Fixes: 83bbc5ac63326433 ("rtc: Add useful timestamp definitions")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
1 file changed