macsec: ensure rx_sa is set when validation is disabled

macsec: ensure rx_sa is set when validation is disabled

Orabug: 25243093

macsec_decrypt() is not called when validation is disabled and so
macsec_skb_cb(skb)->rx_sa is not set; but it is used later in
macsec_post_decrypt(), ensure that it's always initialized.

Fixes: c09440f7dcb3 ("macsec: introduce IEEE 802.1AE driver")
Signed-off-by: Beniamino Galvani <bgalvani@redhat.com>
Acked-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit e3a3b626010a14fe067f163c2c43409d5afcd2a9)
Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>