staging: unisys: Migrate bus from devdata to visor_device

The bus device and regular device were using two different
structs.  Let's combine them as they are not entirely different
from one another.

This allows us to move this creation up the stack later and
actually remove bus/dev_info easily.

Most of the churn is just renaming devdata -> dev and 'struct
visorbus_devdata' to 'struct visor_device'.

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