Enabling drivers from "Devices > Networking" (in menuconfig), for 
example SLIP and/or PLIP, throws link time errors when CONFIG_NET itself 
is =n. Have CONFIG_NETDEVICES depend on CONFIG_NET.
Signed-off-by: NJan Engelhardt <jengelh@gmx.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>