net: dpaa: use __dev_mc_sync in dpaa_set_rx_mode()

net: dpaa: use __dev_mc_sync in dpaa_set_rx_mode()

The original driver first unregisters then re-registers all multicast
addresses in the struct net_device_ops::ndo_set_rx_mode() callback.

As the networking stack calls ndo_set_rx_mode() if a single multicast
address change occurs, a significant amount of time may be used to first
unregister and then re-register unchanged multicast addresses. This
leads to performance issues when tracking large numbers of multicast
addresses.

Replace the unregister and register loop and the hand crafted
mc_addr_list list handling with __dev_mc_sync(), to only update entries
which have changed.

On profiling with an fsl_dpa NIC, this patch presented a speedup of
around 40 when successively setting up 2000 multicast groups using
setsockopt(), without drawbacks on smaller numbers of multicast groups.

Signed-off-by: Jonas Rebmann <jre@pengutronix.de>
Reviewed-by: Sean Anderson <sean.anderson@seco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>