OvmfPkg/Sec: Setup MTRR early in the boot process.
This is v3 of the upstream patch series.
Upstream TDX discussion is not solved yet and probably will not be for a while due to chinese holidays.
Our QE TDX regression testing didn't show any problems, and deadlines are coming closer, so going with this version for rhel-9.4 even though it is not merged yet upstream.