doc: fix flow action command names in testpmd guide
doc: fix flow action command names in testpmd guide

testpmd actions set_tp_src and set_tp_dst documentation adds the
of_ prefix to action names, while the implementation doesn't add it.

This patch removes the prefix from action names in testpmd
documentation.

Fixes: 9ccc94919500 ("ethdev: add flow API actions to modify TCP/UDP port numbers")
Cc: stable@dpdk.org

Signed-off-by: Dekel Peled <f1921780d3213ef78965aec36396441d9bf8894c@mellanox.com>
Acked-by: Ori Kam <dd654df5de18ba542acfaea52fe1a0799392087d@mellanox.com>
Acked-by: Rahul Lakkireddy <3a6b348815dc68871481a310c146a6b821ba8f72@chelsio.com>

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