macsec: set network devtype

The netdevice type structure for macsec was being defined but never used.
To set the network device type the macro SET_NETDEV_DEVTYPE must be called.
Compile tested only, I don't use macsec.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>