net: dsa: mv88e6131: enable hardware bridging

By adding support for bridge operations, FDB operations, and optionally
VLAN operations (for 802.1Q and VLAN filtering aware systems), the
switch bridges ports correctly, the CPU is able to populate the hardware
address databases, and thus hardware bridging becomes functional within
the 88E6185 family of switches.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>