packet: Kill CONFIG_PACKET_MMAP.

Early on this was an experimental facility that few
people other than Alexey Kuznetsov played with.

Now it's a pretty fundamental thing and as people add
more features to AF_PACKET sockets this config options
creates ifdef spaghetti.

So kill it off.

Signed-off-by: David S. Miller <davem@davemloft.net>

net/packet/Kconfig

@@ -14,13 +14,3 @@ config PACKET
 	  be called af_packet.
 
 	  If unsure, say Y.
-
-config PACKET_MMAP
-	bool "Packet socket: mmapped IO"
-	depends on PACKET
-	help
-	  If you say Y here, the Packet protocol driver will use an IO
-	  mechanism that results in faster communication.
-
-	  If unsure, say N.
-