[IPV6]: Make IPV6_SUBTREES depend on IPV6_MULTIPLE_TABLES.

As IPV6_SUBTREES can't work without IPV6_MULTIPLE_TABLES have IPV6_SUBTREES
depend on it.
Signed-off-by: Ville Nuorvala <vnuorval@tcs.hut.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/Kconfig

@@ -175,9 +175,16 @@ config IPV6_TUNNEL
 
 	  If unsure, say N.
 
+config IPV6_MULTIPLE_TABLES
+	bool "IPv6: Multiple Routing Tables"
+	depends on IPV6 && EXPERIMENTAL
+	select FIB_RULES
+	---help---
+	  Support multiple routing tables.
+
 config IPV6_SUBTREES
 	bool "IPv6: source address based routing"
-	depends on IPV6 && EXPERIMENTAL
+	depends on IPV6_MULTIPLE_TABLES
 	---help---
 	  Enable routing by source address or prefix.
 
@@ -189,13 +196,6 @@ config IPV6_SUBTREES
 
 	  If unsure, say N.
 
-config IPV6_MULTIPLE_TABLES
-	bool "IPv6: Multiple Routing Tables"
-	depends on IPV6 && EXPERIMENTAL
-	select FIB_RULES
-	---help---
-	  Support multiple routing tables.
-
 config IPV6_ROUTE_FWMARK
 	bool "IPv6: use netfilter MARK value as routing key"
 	depends on IPV6_MULTIPLE_TABLES && NETFILTER