Ovmf/ResetVector: Simplify and consolidate the SEV features checks

Ovmf/ResetVector: Simplify and consolidate the SEV features checks

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

Simplify and consolidate the SEV and SEV-ES checks into a single routine.
This new routine will use CPUID to check for the appropriate CPUID leaves
and the required values, as well as read the non-interceptable SEV status
MSR (0xc0010131) to check SEV and SEV-ES enablement.

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: <43a660624c32b5f6c2610bf42ee39101c21aff68.1610045305.git.thomas.lendacky@amd.com>