efi_loader: handling of daylight saving time

If SetTime() is meant to set daylight saving time it will be called with
Time.Daylight == EFI_TIME_ADJUST_DAYLIGHT | EFI_TIME_IN_DAYLIGHT.

Return 0 from GetTime() if time is not in daylight because we cannot
determine if we are in a time zone with daylight saving time.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>