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.