i386/sev: Add support for populating OVMF metadata pages

i386/sev: Add support for populating OVMF metadata pages

OVMF reserves various pages so they can be pre-initialized/validated
prior to launching the guest. Add support for populating these pages
with the expected content.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Co-developed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Signed-off-by: Pankaj Gupta <pankaj.gupta@amd.com>
Message-ID: <20240530111643.1091816-20-pankaj.gupta@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>