staging: unisys: visorbus: remove unused chipsetready information

Chipsetready sysfs entry is not used by any guests or service
partitions.

remove unused g_chipset_msg_hdr our service partition

remove unused chipsetready_store and driver attributes:
        chipsetready_store()
        visorchipset_guest_attrs
        visorchipset_guest_groupw

remove unused chipsets_events:
        check_chipset_events()
        clear_chipset_events()
        visorchipset_holdchipsetready

remove sysfs documentation dealing with chipsetready

Signed-off-by: Erik Arfvidson <erik.arfvidson@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>