staging: unisys: visorinput: change input bus type to BUS_VIRTUAL (6)

BUS_HOST wasn't really appropriate, so I changed to BUS_VIRTUAL, which is
what virtio uses.

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>