Fix some statements in disc(4) and about it:

- ifnet is no more embedded in softc;
- the interface name is `disc', not `ds'.

sys/conf/NOTES

@@ -736,7 +736,7 @@ device		mn	# Munich32x/Falc54 Nx64kbit/sec cards.
 #  simultaneous BPF clients programs runnable.  DHCP requires bpf.
 #  The `disc' device implements a minimal network interface,
 #  which throws away all packets sent and never receives any.  It is
-#  included for testing purposes.  This shows up as the `ds' interface.
+#  included for testing and benchmarking purposes.
 #  The `edsc' device implements a minimal Ethernet interface,
 #  which discards all packets sent and receives none.
 #  The `tap' device is a pty-like virtual Ethernet interface
@@ -783,7 +783,7 @@ device		arcnet			#Generic Arcnet
 device		sppp			#Generic Synchronous PPP
 device		loop			#Network loopback device
 device		bpf			#Berkeley packet filter
-device		disc			#Discard device (ds0, ds1, etc)
+device		disc			#Discard device based on loopback
 device		edsc			#Ethernet discard device
 device		tap			#Virtual Ethernet driver
 device		tun			#Tunnel driver (ppp(8), nos-tun(8))

sys/net/if_disc.c

@@ -62,7 +62,7 @@
 #define DISCNAME	"disc"
 
 struct disc_softc {
-	struct ifnet *sc_ifp;	/* must be first */
+	struct ifnet *sc_ifp;
 };
 
 static int	discoutput(struct ifnet *, struct mbuf *,