examples/l3fwd: fix using packet type blindly

examples/l3fwd: fix using packet type blindly

As a example to use ptype info, l3fwd needs firstly to use
rte_eth_dev_get_supported_ptypes() API to check if device and/or
its PMD driver will parse and fill the needed packet type; if not,
use the newly added option, --parse-ptype, to analyze it in the
callback softly.

As the mode of EXACT_MATCH uses the 5 tuples to caculate hash, so
we narrow down its scope to:
  a. ip packets with no extensions, and
  b. L4 payload should be either tcp or udp.

Note: this patch does not completely solve the issue, "cannot run
l3fwd on virtio or other devices", because hw_ip_checksum may be
not supported by the devices. Currently we can:
  a. remove this requirements, or
  b. wait for virtio front end (pmd) to support it.

Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>