staging: dpaa2-switch: add fast-ageing on bridge leave

Upon leaving a bridge, any MAC addresses learnt on the switch port prior
to this point have to be removed so that we preserve the bridging domain
configuration.

Restructure the dpaa2_switch_port_fdb_dump() function in order to have a
common dpaa2_switch_fdb_iterate() function between the FDB dump callback
and the fast age procedure. To accomplish this, add a new callback -
dpaa2_switch_fdb_cb_t - which will be called on each MAC addr and,
depending on the situation, will either dump the FDB entry into a
netlink message or will delete the address from the FDB table, in case
of the fast-age.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>