If STP is active, this setting is applied on bridged ports each time an
Ethernet link is established (topology changes).

Since the setting is global to the switch and a reset is required to
change it, resets are prevented if the new callback does not change the
value that the hardware already is programmed for.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>