doc, net: Remove obsolete reference to dev->poll

Commit bea3348e ('[NET]: Make NAPI
polling independent of struct net_device objects.') removed the
automatic disabling of NAPI polling by dev_close(), and drivers
must now do this themselves.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/networking/netdevices.txt

@@ -54,8 +54,7 @@ dev->open:
 dev->stop:
 	Synchronization: rtnl_lock() semaphore.
 	Context: process
-	Note1: netif_running() is guaranteed false
-	Note2: dev->poll() is guaranteed to be stopped
+	Note: netif_running() is guaranteed false
 
 dev->do_ioctl:
 	Synchronization: rtnl_lock() semaphore.