staging: unisys: visornic: delay start of worker thread until netdev created

This only makes sense, since the worker thread depends upon the netdev
existing.

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>