i386/sev: Add handling to encrypt/finalize guest launch data

i386/sev: Add handling to encrypt/finalize guest launch data

Process any queued up launch data and encrypt/measure it into the SNP
guest instance prior to initial guest launch.

This also updates the KVM_SEV_SNP_LAUNCH_UPDATE call to handle partial
update responses.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Co-developed-by: Michael Roth <michael.roth@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: <20240530111643.1091816-17-pankaj.gupta@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>