app/testpmd: remove useless function declarations
app/testpmd: remove useless function declarations

The four function declarations have no function implementation,
remove them.

Fixes: 0db70a803028 ("app/testpmd: add commands for filters")
Cc: stable@dpdk.org

Signed-off-by: Zhiyong Yang <fbdb847fac8e5e50b588eb93d9ff9fd811b7568c@intel.com>

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