net: dsa: microchip: add MIB counter reading support
Add background MIB counter reading support.
Port MIB counters should only be read when there is link. Otherwise it is
a waste of time as hardware never increases those counters. There are
exceptions as some switches keep track of dropped counts no matter what.
Signed-off-by: Tristram Ha <Tristram.Ha@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>