target/i386/sev: sev_get_attestation_report use g_autofree

target/i386/sev: sev_get_attestation_report use g_autofree

Removes a whole bunch of g_free's and a goto.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Connor Kuehl <ckuehl@redhat.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
Message-Id: <20210603113017.34922-1-dgilbert@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20211007161716.453984-12-philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>