m68knommu: fix default starting date

Currently m68knommu boards without RTC chip start with an unexpected
default date of 1999-11-30 (Actually the source asks for 2000-00-00)
Make that 1970-01-01 instead, as expected.

Signed-off-by: Philippe De Muyter <phdm@macqel.be>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>