net: introduce the MACSEC netdev feature

This patch introduce a new netdev feature, which will be used by drivers
to state they can perform MACsec transformations in hardware.

The patchset was gathered by Mark, macsec functinality itself
was implemented by Dmitry, Mark and Pavel Belous.

Signed-off-by: Antoine Tenart <antoine.tenart@bootlin.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>