net: ethtool: Add destination MAC address to flow steering API

Add ability to specify destination MAC address for L3/L4 flow spec
in order to be able to specify action for different VM's under vSwitch
configuration. This change is transparent to older userspace.

Signed-off-by: Yan Burman <yanb@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>