Merge branch 'ag71xx-add-ethtool-and-flow-control-support'

Oleksij Rempel says:

====================
ag71xx: add ethtool and flow control support

The main target of this patches is to provide flow control support
for ag71xx driver. To be able to validate this functionality, I also
added ethtool support with HW counters. So, this patches was validated
with iperf3 and counters showing Pause frames send or received by this
NIC.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>