net: phy: nxp-c45-tja11xx: add MACsec support

Add MACsec support.
The MACsec block has four TX SCs and four RX SCs. The driver supports up
to four SecY. Each SecY with one TX SC and one RX SC.
The RX SCs can have two keys, key A and key B, written in hardware and
enabled at the same time.
The TX SCs can have two keys written in hardware, but only one can be
active at a given time.
On TX, the SC is selected using the MAC source address. Due of this
selection mechanism, each offloaded netdev must have a unique MAC
address.
On RX, the SC is selected by SCI(found in SecTAG or calculated using MAC
SA), or using RX SC 0 as implicit.

Signed-off-by: Radu Pirea (NXP OSS) <radu-nicolae.pirea@oss.nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>