staging: unisys: Removed unused entries from struct visor_channeltype_descriptor

min_size/max_size aren't used anywhere, and they were just causing
headaches in the drivers being ported over to the new interfaces.

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>