module: Rename machine_init() to opts_init()

module: Rename machine_init() to opts_init()

The only remaining users of machine_init() only call
qemu_add_opts(). Rename machine_init() to opts_init() and move it
closer to the qemu_add_opts() calls on vl.c.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>