net: atlantic: macsec: clear encryption keys from the stack

Commit aaab73f8 ("macsec: clear encryption keys from the stack after
setting up offload") made sure to clean encryption keys from the stack
after setting up offloading, but the atlantic driver made a copy and did
not clear it. Fix this.

[4 Fixes tags below, all part of the same series, no need to split this]

Fixes: 9ff40a75 ("net: atlantic: MACSec ingress offload implementation")
Fixes: b8f8a0b7 ("net: atlantic: MACSec ingress offload HW bindings")
Fixes: 27736563 ("net: atlantic: MACSec egress offload implementation")
Fixes: 9d106c6d ("net: atlantic: MACSec egress offload HW bindings")
Signed-off-by: Antoine Tenart <atenart@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>