qemu-options: document missing memory-backend-file options

This patch adds undocumented memory-backend-file options to the
documentation.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20171128161529.3025-2-stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
1 file changed