app/testpmd: enable fast free Tx offload by default
app/testpmd: enable fast free Tx offload by default

Enable the DEV_TX_OFFLOAD_MBUF_FAST_FREE in case the underlying device
supports.

This is to preserve the previous offloads configuration made according
to the PMD defaults.

Signed-off-by: Shahaf Shuler <59427d49da6f2b944fbf4cb5ee70ef3ac25f744f@mellanox.com>
Acked-by: Wenzhuo Lu <58cb9036bdff9a5412edc3b9f70e105ccf59954f@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk