machine: make memory-backend a link property

Handle HostMemoryBackend creation and setting of ms->ram entirely in
machine_run_board_init.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220414165300.555321-5-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
5 files changed