net/mlx5e: Add MACsec RX steering rules

Rx flow steering consists of two flow tables (FTs).

The first FT (crypto table) have one default miss rule so non MACsec
offloaded packets bypass the MACSec tables.
All others flow table entries (FTEs) are divided to two equal groups
size, both of them are for MACsec packets:
The first group is for MACsec packets which contains SCI field in the
SecTAG header.
The second group is for MACsec packets which doesn't contain SCI,
where need to match on the source MAC address (only if the SCI
is built from default MACsec port).
Destination MAC address, ethertype and some of SecTAG fields
are also matched for both groups.
In case of match, invoke decrypt action on the packet.
For each MACsec Rx offloaded SA two rules are created: one with SCI
and one without SCI.

The second FT (check table) has two fixed rules:
One rule is for verifying that the previous offload actions were
finished successfully.
In this case, need to decap the SecTAG header and forward the packet
for further processing.
Another default rule for dropping packets that failed in the previous
decrypt actions.

The MACsec FTs are created on demand when the first MACsec rule is
added and destroyed when the last MACsec rule is deleted.

Signed-off-by: Lior Nahmanson <liorna@nvidia.com>
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>