Move the MODULE_DEVICE_TABLE macro to module.h where it belongs
in preparation for different bus (e.g., USB, SDIO) support.
The various struct <bus>_device_id, if not elsewhere, should be
defined in mod_devicetable.h.
This is the next step after 2f5666c1727c.
No functional changes.
Sponsored by: The FreeBSD Foundation
MFC after: 3 days