fw_cfg: move QOM type defines and fw_cfg types into fw_cfg.h

By exposing FWCfgIoState and FWCfgMemState internals we allow the possibility
for the internal MemoryRegion fields to be mapped by name for boards that wish
to wire up the fw_cfg device themselves.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <1500025208-14827-4-git-send-email-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
