Silicon/Qemu: use 64-bit Pcds for SbsaQemu GIC addresses

gArmTokenSpaceGuid.PcdGicDistributorBase and
gArmTokenSpaceGuid.PcdGicRedistributorsBase are both defined as UINT64 in
ArmPkg.dec, but SbsaQemuAcpiDxe and its exported header file use
PcdGet32. While this currently works, it will break once these Pcds are
made dynamic - so fix.

Signed-off-by: Leif Lindholm <quic_llindhol@quicinc.com>
Reviewed-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Graeme Gregory <graeme@xora.org.uk>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Graeme Gregory <graeme@xora.org.uk>
Cc: Radoslaw Biernacki <rad@semihalf.com>
Cc: Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>