net/mlx5e: Fix macsec possible null dereference when updating MAC security entity (SecY)

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: Fix macsec possible null dereference when updating MAC security entity (SecY) Upon updating MAC security entity (SecY) in hw offload path, the macsec security association (SA) initialization routine is called. In case of extended packet number (epn) is enabled the salt and ssci attributes are retrieved using the MACsec driver rx_sa context which is unavailable when updating a SecY property such as encoding-sa hence the null dereference. Fix by using the provided SA to set those attributes.