net/ncsi: Fix AEN HNCDSC packet length

Correct the value of the HNCDSC AEN packet.
Fixes: 7a82ecf4

 "net/ncsi: NCSI AEN packet handler"

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>