examples/ip_fragmentation: fix Tx queues init

examples/ip_fragmentation: fix Tx queues init

The application tries to configure queue ids larger
than the maximum allowed by MAX_TX_QUEUE_PER_PORT. This
causes the startup error:

"
  ...
  Initializing port 0 on lcore 0... Address:7C:FE:90:12:23:0D
  txq=0,0 txq=1,1 txq=2,2 txq=3,3 txq=4,4 txq=5,5 txq=6,6 txq=7,7 txq=8,8
  txq=9,9 txq=10,10 txq=11,11 txq=12,12 txq=13,13 txq=14,14 txq=15,15
  txq=16,16 Invalid TX queue_id=16

  EAL: Error - exiting with code: 1
    Cause: rte_eth_tx_queue_setup: err=-22, port=0
"

The error reproduces when lcores aren't set, and when the
machine has more than 16 cores.

Fixes: af75078fece3 ("first public release")
Cc: stable@dpdk.org
Signed-off-by: Ali Alnubani <alialnu@mellanox.com>