Make the whole netdevices menu depend on NET, rather than having an empty
submenu when networking is disabled.

Indeed, almost the whole body of the menu was surrounded by if NETDEVICES,
and what was outside depended on NETCONSOLE which is inside the menu.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>