net: dsa: mv88e6xxx: Fix stats counters for 6352 family

net: dsa: mv88e6xxx: Fix stats counters for 6352 family

The statistic counters for the mv88e6172 never worked. This device is
a member of the 6352 family of chips, which has a slightly different
layout of the register used for capturing statistics. Add support for
detecting this family and poking the port in the right place in the
register.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>