staging: unisys: Remove num_visornic_open array

As pointed out in a recent review, the num_visornic_open array didn't do
anything useful, and it exposed a potential race in the visornic code that
could arise while taking down a net interface while reading from the
debugfs files. Fix that by removing the array entirely, and just iterating
over all the registered netdevs in a given namespace, filtering on them
having visornic ops (to identify which are ours), and having their queues
not be stopped (identifying that they are up). This should prevent any oops
conditions happening due to changing state in that array, and save us a
bunch of code too.
Signed-off-by: Neil Horman <nhorman@redhat.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>