OvmfPkg/PlatformInitLib: Differentiate TDX case for Cloud Hypervisor

OvmfPkg/PlatformInitLib: Differentiate TDX case for Cloud Hypervisor

Rely on the CcProbe() function to identify when running on TDX. This
allows the firmware to follow a different codepath for Cloud Hypervisor,
which means it doesn't rely on PVH to find out about memory below 4GiB.
instead it falls back onto the CMOS to retrieve that information.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Reviewed-by: Min Xu <min.m.xu@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>