staging: unisys: Convert bus creation to use visor_device

This patch removes the legacy bus_info struct and instead creates
and passes around a traditional struct device.

This allows us to remove a lot of the various look up code and
removes the doubt if the struct exists or not.

Half of the churn is just the conversion of visorchipset_bus_info
to visor_device.  Various cleanups include re-arranging the failure
paths to make more sense.

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>