doc: Clarify behavior when sysctl tcp_ecn = 1

Recent commit (commit 7e3a2dc52953 doc: make the description of how tcp_ecn
works more explicit and clear ) clarified the behavior of tcp_ecn sysctl
variable but description is inconsistent. When requested by incoming conections,
ECN is enabled with not just tcp_ecn = 2 but also with tcp_ecn = 1.

This patch makes it clear that with tcp_ecn = 1, ECN is enabled when requested
by incoming connections.

Also fix spelling of 'incoming'.

Signed-off-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/ip-sysctl.txt

@@ -214,8 +214,9 @@ tcp_ecn - INTEGER
 	congestion before having to drop packets.
 	Possible values are:
 		0 Disable ECN.  Neither initiate nor accept ECN.
-		1 Always request ECN on outgoing connection attempts.
-		2 Enable ECN when requested by incomming connections
+		1 Enable ECN when requested by incoming connections and
+		  also request ECN on outgoing connection attempts.
+		2 Enable ECN when requested by incoming connections
 		  but do not request ECN on outgoing connections.
 	Default: 2