This function appeared previously unused (called only from rtc_display, also unused),
but it returned an incorrect weekday. Change the algorithm to use Zeller's Rule, a
well-known algorithm for calculuating weekdays.
Change-Id: Ibce6822942f8d9d9f39c2b6065cd785dca9e8e09
Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-on: https://review.coreboot.org/c/31557
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
b47c633c31