macsec: add rcu_barrier() on module exit

macsec: add rcu_barrier() on module exit

Without this, the various uses of call_rcu could cause a kernel panic.

Fixes: c09440f7dcb3 ("macsec: introduce IEEE 802.1AE driver")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit b196c22af5c3ff784c472c80f6fb4e5fad67b2ac)

Orabug: 24614549

Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>