dummy: documentation is stale

dummy0/1/2 names are always used and there are options to set multiple
dummy devices. Remove the obsolete text

Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=42865
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/Kconfig

@@ -66,10 +66,7 @@ config DUMMY
 	  <http://www.tldp.org/docs.html#guide>.
 
 	  To compile this driver as a module, choose M here: the module
-	  will be called dummy.  If you want to use more than one dummy
-	  device at a time, you need to compile this driver as a module.
-	  Instead of 'dummy', the devices will then be called 'dummy0',
-	  'dummy1' etc.
+	  will be called dummy.
 
 config EQUALIZER
 	tristate "EQL (serial line load balancing) support"