OvmfPkg/ResetVector: Perform a simple SEV-ES sanity check

OvmfPkg/ResetVector: Perform a simple SEV-ES sanity check

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3108

If a hypervisor incorrectly reports through CPUID that SEV-ES is not
active, ensure that a #VC exception was not taken. If it is found that
a #VC was taken, then the code enters a HLT loop.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <afa2030b95b852313b13982df82d472187e59b92.1610045305.git.thomas.lendacky@amd.com>