staging: unisys: visornic: prevent hang doing 'modprobe -r visornic'

A stray+extraneous 'netif_napi_add()' that we were doing in
visornic_probe() was causing havoc when we got into visornic_remove(),
called during 'modprobe -r visornic'. The symptom was a processor busy-wait
loop on the modprobe process, which '/proc/<pid>/stack' would show looping
doing napi things.

Presumably the stray line got there as a result of some merging snafoo, and
has been deleted to fix the problem. With this patch 'modprobe -r visornic'
and a subsequent 'modprobe visornic' both complete successfully, and result
in an operational network.

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>