ArmVirtualizationPkg/ArmVirtualizationQemu: enable IO addressing

ArmVirtualizationPkg/ArmVirtualizationQemu: enable IO addressing

Set gEmbeddedTokenSpaceGuid.PcdPrePiCpuIoSize to 16, which determines the
maximum "I/O address width".

This ensures, through the BuildCpuHob() call in
"ArmPkg/Drivers/CpuPei/CpuPei.c", that the inital I/O Space Map will
consist of a 16-bit wide "splittable" entry, when the DXE core starts (see
CoreInitializeGcdServices() in "MdeModulePkg/Core/Dxe/Gcd/Gcd.c"):

  GCD:Initial GCD I/O Space Map
  GCDIoType  Range
  ========== =================================
  NonExist   0000000000000000-000000000000FFFF

Otherwise this range would have size 0, and (since it could not be split)
any gDS->AddIoSpace() calls would fail.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Olivier Martin <Olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16902 6f19259b-4bc3-4df7-8a09-765794883524