Only override the time offset in rtcinfo[0] when setting the time; don't

Only override the time offset in rtcinfo[0] when setting the time; don't
touch rtcinfo[1] and rtcinfo[2].  This doesn't actually fix anything
but rtcinfo[1] on a new machine already contains the value we write into
it and we don't really know what the other bits are used for.

ok patrick@