OvmfPkg: PlatformPei: create the CPU HOB with dynamic memory space width

OvmfPkg: PlatformPei: create the CPU HOB with dynamic memory space width

Maoming reported that guest memory sizes equal to or larger than 64GB
were not correctly handled by OVMF.

Enabling the DEBUG_GCD (0x00100000) bit in PcdDebugPrintErrorLevel, and
starting QEMU with 64GB guest RAM size, I found the following error in the
OVMF debug log:

> GCD:AddMemorySpace(Base=0000000100000000,Length=0000000F40000000)
>   GcdMemoryType   = Reserved
>   Capabilities    = 030000000000000F
>   Status = Unsupported

This message is emitted when the DXE core is initializing the memory space
map, processing the "above 4GB" memory resource descriptor HOB that was
created by OVMF's QemuInitializeRam() function (see "UpperMemorySize").

The DXE core's call chain fails in:

CoreInternalAddMemorySpace() [MdeModulePkg/Core/Dxe/Gcd/Gcd.c]
  CoreConvertSpace()
    //
    // Search for the list of descriptors that cover the range BaseAddress
    // to BaseAddress+Length
    //
    CoreSearchGcdMapEntry()

CoreSearchGcdMapEntry() fails because the one entry (with type
"nonexistent") in the initial GCD memory space map is too small, and
cannot be split to cover the memory space range being added:

> GCD:Initial GCD Memory Space Map
> GCDMemType Range                             Capabilities     Attributes
> ========== ================================= ================ ================
> NonExist   0000000000000000-0000000FFFFFFFFF 0000000000000000 0000000000000000

The size of this initial entry is determined from the CPU HOB
(CoreInitializeGcdServices()).

Set the SizeOfMemorySpace field in the CPU HOB to mPhysMemAddressWidth,
which is the narrowest valid value to cover the entire guest RAM.

Reported-by: Maoming <maoming.maoming@huawei.com>
Cc: Maoming <maoming.maoming@huawei.com>
Cc: Huangpeng (Peter) <peter.huangpeng@huawei.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Wei Liu <wei.liu2@citrix.com>
Tested-by: Maoming <maoming.maoming@huawei.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17720 6f19259b-4bc3-4df7-8a09-765794883524