TCP: update ip_local_port_range documentation

The explanation of ip_local_port_range in
Documentation/networking/ip-sysctl.txt contains several factual
errors:

- The default value of ip_local_port_range does not depend on the
  amount of memory available in the system.
- tcp_tw_recycle is not enabled by default.
- 1024-4999 is not the default value.
- Etc.

Clean up the mess.
Signed-off-by: NFernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/networking/ip-sysctl.txt

@@ -604,15 +604,8 @@ IP Variables:
 ip_local_port_range - 2 INTEGERS
 	Defines the local port range that is used by TCP and UDP to
 	choose the local port. The first number is the first, the
-	second the last local port number. Default value depends on
-	amount of memory available on the system:
-	> 128Mb 32768-61000
-	< 128Mb 1024-4999 or even less.
-	This number defines number of active connections, which this
-	system can issue simultaneously to systems not supporting
-	TCP extensions (timestamps). With tcp_tw_recycle enabled
-	(i.e. by default) range 1024-4999 is enough to issue up to
-	2000 connections per second to systems supporting timestamps.
+	second the last local port number. The default values are
+	32768 and 61000 respectively.
 
 ip_local_reserved_ports - list of comma separated ranges
 	Specify the ports which are reserved for known third-party