staging: unisys: remove redundant variable

remove the variable "registered", which was used in the cleanup() to
detect if the driver has successfully initialized. the cleanup()
is called from module_exit, so its obvious that the module has
successfully initialized. if the initialization had failed, then
we will never be in the cleanup().

Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>