ich9: fix skipped vmstate_memhp_state subsection

By declaring another .subsections array for vmstate_tco_io_state made
vmstate_memhp_state not registered anymore. There must be only one
.subsections array for all subsections.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Amit Shah <amit.shah@redhat.com>
Reported-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Paulo Alcantara <pcacjr@zytor.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>