[PKTGEN]: Remove an unused definition in pktgen.c.

[PKTGEN]: Remove an unused definition in pktgen.c.

- Remove an unused definition (LAT_BUCKETS_MAX) in net/core/pktgen.c.
- Remove the corresponding comment.
- The LAT_BUCKETS_MAX seems to have to do with a patch from a long
time ago which was not applied (Ben Greear), which dealt with latency
counters.

See, for example : http://oss.sgi.com/archives/netdev/2002-09/msg00184.html

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>