ArmVirtPkg/PlatformHasAcpiDtDxe: depend on gEfiVariableArchProtocolGuid

ArmVirtPkg/PlatformHasAcpiDtDxe: depend on gEfiVariableArchProtocolGuid

PlatformHasAcpiDtDxe consumes the DynamicHii PCD called
"gArmVirtTokenSpaceGuid.PcdForceNoAcpi". The PcdGetBool() library call
terminates in gRT->GetVariable(), in the MdeModulePkg/Universal/PCD/Dxe
driver. Put "gEfiVariableArchProtocolGuid" on PlatformHasAcpiDtDxe's DEPEX
so that we not attempt the call before the PCD driver can successfully
read non-volatile variables.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Supreeth Venkatesh <Supreeth.Venkatesh@arm.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>