sev/i386: Add initial support for SEV-ES

sev/i386: Add initial support for SEV-ES

Provide initial support for SEV-ES. This includes creating a function to
indicate the guest is an SEV-ES guest (which will return false until all
support is in place), performing the proper SEV initialization and
ensuring that the guest CPU state is measured as part of the launch.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Co-developed-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Message-Id: <2e6386cbc1ddeaf701547dd5677adf5ddab2b6bd.1611682609.git.thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>