Remove link state change callback handler. There is no need to

Remove link state change callback handler.  There is no need to
register both status change and link state change callbacks.
Implement checking valid link in state change callback and poll
active link state in vr_tick().  This allows immediate detection of
lost link as well as protecting driver from frequent link flips during
link renegotiation.  taskq implementation was removed because driver
now needs to poll link state in vr_tick().
While I'm here do not report current link state if interface is not
running.

Tested by:	n_hibma
MFC after:	1 week