Marvell/Drivers: MvFvbDxe: Switch to PcdSet64S

According to the bug:
https://bugzilla.tianocore.org/show_bug.cgi?id=2777


the deprecated code under DISABLE_NEW_DEPRECATED_INTERFACES
will be removed, which will result in compilation breakage
of the Marvell platforms. Prevent that by switching to the
different PcdSet API.

Signed-off-by: Marcin Wojtas <mw@semihalf.com>
Reviewed-by: Leif Lindholm <leif@nuviainc.com>