samples/pktgen: Correct comments about the thread config

They all claimed to be two CPU examples using eth1, eth2 but
that is only true in one case!

Rob Jones pointed out spelling and grammar errors here, which I've
also corrected.

Cc: Rob Jones <rob.jones@codethink.co.uk>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/samples/pktgen/pktgen.conf-1-2 b/samples/pktgen/pktgen.conf-1-2
index 7f6e88e..136e10c 100755
--- a/samples/pktgen/pktgen.conf-1-2
+++ b/samples/pktgen/pktgen.conf-1-2
@@ -18,7 +18,7 @@
 
 
 # thread config
-# One CPU means one thread. One CPU exammple. We add eth1, eth2 respectivly.
+# One CPU means one thread. One CPU example. We add eth1, eth2 respectivly.
 
 PGDEV=/proc/net/pktgen/kpktgend_0
   echo "Removing all devices"