[INET_DIAG]: Move the tcp_diag interface to the proper place

With this the previous setup is back, i.e. tcp_diag can be built as a module,
as dccp_diag and both share the infrastructure available in inet_diag.

If one selects CONFIG_INET_DIAG as module CONFIG_INET_TCP_DIAG will also be
built as a module, as will CONFIG_INET_DCCP_DIAG, if CONFIG_IP_DCCP was
selected static or as a module, if CONFIG_INET_DIAG is y, being statically
linked CONFIG_INET_TCP_DIAG will follow suit and CONFIG_INET_DCCP_DIAG will be
built in the same manner as CONFIG_IP_DCCP.

Now to aim at UDP, converting it to use inet_hashinfo, so that we can use
iproute2 for UDP sockets as well.

Ah, just to show an example of this new infrastructure working for DCCP :-)

[root@qemu ~]# ./ss -dane
State      Recv-Q Send-Q Local Address:Port  Peer Address:Port
LISTEN     0      0                  *:5001             *:*     ino:942 sk:cfd503a0
ESTAB      0      0          127.0.0.1:5001     127.0.0.1:32770 ino:943 sk:cfd50a60
ESTAB      0      0          127.0.0.1:32770    127.0.0.1:5001  ino:947 sk:cfd50700
TIME-WAIT  0      0          127.0.0.1:32769    127.0.0.1:5001  timer:(timewait,3.430ms,0) ino:0 sk:cf209620

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index 019e88d..e55136a 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -413,8 +413,8 @@
 	  
 	  If unsure, say Y.
 
-config IP_INET_DIAG
-	tristate "IP: INET socket monitoring interface"
+config INET_DIAG
+	tristate "INET: socket monitoring interface"
 	default y
 	---help---
 	  Support for INET (TCP, DCCP, etc) socket monitoring interface used by
@@ -423,6 +423,10 @@
 	  
 	  If unsure, say Y.
 
+config INET_TCP_DIAG
+	depends on INET_DIAG
+	def_tristate INET_DIAG
+
 config TCP_CONG_ADVANCED
 	bool "TCP: advanced congestion control"
 	---help---