[IPV4]: Move FIB lookup algorithm choice under IP_ADVANCED_ROUTING

Most users need not be concerned with a complex choice of what
FIB lookup algorithm to use.  So give them the safe default of
IP_FIB_HASH if IP_ADVANCED_ROUTING is disabled.
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/Kconfig

 #
 # IP configuration
 #
-choice 
-	prompt "Choose IP: FIB lookup"
-	depends on INET
-	default IP_FIB_HASH
-
-config IP_FIB_HASH
-	bool "FIB_HASH"
-	---help---
-	Current FIB is very proven and good enough for most users.
-
-config IP_FIB_TRIE
-	bool "FIB_TRIE"
-	---help---
-	Use new experimental LC-trie as FIB lookup algoritm. 
-        This improves lookup performance
-	
-	LC-trie is described in:
-	
- 	IP-address lookup using LC-tries. Stefan Nilsson and Gunnar Karlsson
- 	IEEE Journal on Selected Areas in Communications, 17(6):1083-1092, June 1999
-	An experimental study of compression methods for dynamic tries
- 	Stefan Nilsson and Matti Tikkanen. Algorithmica, 33(1):19-33, 2002.
- 	http://www.nada.kth.se/~snilsson/public/papers/dyntrie2/
-       
-endchoice
-
 config IP_MULTICAST
 	bool "IP: multicasting"
 	depends on INET
@@ -79,6 +53,44 @@ config IP_ADVANCED_ROUTER
 
 	  If unsure, say N here.
 
+choice 
+	prompt "Choose IP: FIB lookup algorithm (choose FIB_HASH if unsure)"
+	depends on IP_ADVANCED_ROUTER
+	default IP_FIB_HASH
+
+config IP_FIB_HASH
+	bool "FIB_HASH"
+	---help---
+	Current FIB is very proven and good enough for most users.
+
+config IP_FIB_TRIE
+	bool "FIB_TRIE"
+	---help---
+	Use new experimental LC-trie as FIB lookup algoritm. 
+        This improves lookup performance if you have a large
+	number of routes.
+
+	LC-trie is a longest matching prefix lookup algorithm which
+	performs better than FIB_HASH for large routing tables.
+	But, it consumes more memory and is more complex.
+	
+	LC-trie is described in:
+	
+ 	IP-address lookup using LC-tries. Stefan Nilsson and Gunnar Karlsson
+ 	IEEE Journal on Selected Areas in Communications, 17(6):1083-1092, June 1999
+	An experimental study of compression methods for dynamic tries
+ 	Stefan Nilsson and Matti Tikkanen. Algorithmica, 33(1):19-33, 2002.
+ 	http://www.nada.kth.se/~snilsson/public/papers/dyntrie2/
+       
+endchoice
+
+# If the user does not enable advanced routing, he gets the safe
+# default of the fib-hash algorithm.
+config IP_FIB_HASH
+	bool
+	depends on !IP_ADVANCED_ROUTER
+	default y
+
 config IP_MULTIPLE_TABLES
 	bool "IP: policy routing"
 	depends on IP_ADVANCED_ROUTER