Marvell: RealTimeClockLib: Fix daylight and timezone handling

The Marvell implementation of the RealTimeClockLib was unnecessarily
overriding the daylight and timezone values, which are handled
by non-volatile variables in the generic code. Fix that.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>