OvmfPkg: Add support for memory above 4GB

When QEMU has more than 3.5GB of RAM, it will map the
additional memory above 4GB.  This change will make that
RAM accessible to OVMF.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@11266 6f19259b-4bc3-4df7-8a09-765794883524
3 files changed