app/testpmd: support displaying 32-byte Rx descriptors

app/testpmd: support displaying 32-byte Rx descriptors

i40e supports both 16 and 32 bytes RX descriptors, while ixgbe and
igb support 16 bytes size only. Code changes have been made in
test-pmd to support both 16 and 32 bytes RX descriptors according
to the configuration in config files.

Signed-off-by: Helin Zhang <helin.zhang@intel.com>
Signed-off-by: Jing Chen <jing.d.chen@intel.com>
Acked-by: Cunming Liang <cunming.liang@intel.com>
Acked-by: Jijiang Liu <jijiang.liu@intel.com>
Acked-by: Jingjing Wu <jingjing.wu@intel.com>
Acked-by: Heqing Zhu <heqing.zhu@intel.com>
Tested-by: Waterman Cao <waterman.cao@intel.com>