staging: unisys: Convert device functions to pass dev_info pointer around

Most device functions pass bus_no and dev_no around and then do a lookup
inside each function to find the dev_info struct.  Instead just pass the
pointer.

This prepares us for a later conversion to using visor device.

No real technical changes.  Just function header changes and little
cleanups as a result.

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>