staging: unisys: Eliminate visor_memregion_write()

visorchannel's signal code should call visorchannel_write() directly.
This is more consistent and cleaner, and allows us to remove the last
memregion call.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>