macsec: don't increment counters for an unrelated SA

On RX, we shouldn't be incrementing the stats for an arbitrary SA in
case the actual SA hasn't been set up. Those counters are intended to
track packets for their respective AN when the SA isn't currently
configured. Due to the way MACsec is implemented, we don't keep
counters unless the SA is configured, so we can't track those packets,
and those counters will remain at 0.

The RXSC's stats keeps track of those packets without telling us which
AN they belonged to. We could add counters for non-existent SAs, and
then find a way to integrate them in the dump to userspace, but I
don't think it's worth the effort.

Fixes: 91ec9bd5 ("macsec: Fix traffic counters/statistics")
Reported-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://patch.msgid.link/f5ac92aaa5b89343232615f4c03f9f95042c6aa0.1728657709.git.sd@queasysnail.net


Signed-off-by: Jakub Kicinski <kuba@kernel.org>