arp_notify: document that a gratuitous ARP request is sent when this option is enabled

This option causes a gratuitous ARP request, not a reply as the documentation
currently suggests.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Stephen Hemminger <shemminger@linux-foundation.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/ip-sysctl.txt

@@ -903,7 +903,7 @@ arp_ignore - INTEGER
 arp_notify - BOOLEAN
 	Define mode for notification of address and device changes.
 	0 - (default): do nothing
-	1 - Generate gratuitous arp replies when device is brought up
+	1 - Generate gratuitous arp requests when device is brought up
 	    or hardware address changes.
 
 arp_accept - BOOLEAN