networking: NET_CLS_ROUTE4 depends on INET

IP_ROUTE_CLASSID depends on INET and NET_CLS_ROUTE4 selects
IP_ROUTE_CLASSID, but when INET is not enabled, this kconfig warning
is produced, so fix it by making NET_CLS_ROUTE4 depend on INET.

warning: (NET_CLS_ROUTE4) selects IP_ROUTE_CLASSID which has unmet direct dependencies (NET && INET)

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>