net: macsec: allow multiple macsec devices with offload

Offload engine can setup several SecY. Each macsec interface shall have
its own mac address. It will filter a traffic by dest mac address.

Signed-off-by: Dmitry Bogdanov <dbogdanov@marvell.com>
Signed-off-by: Mark Starovoytov <mstarovoitov@marvell.com>
Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>