staging: unisys: Embed struct device for easier handling of attr

Handling the sysfs attributes become easier to deal with when you can just
run container_of(dev) to get devdata.

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>