app/testpmd: add commands for filters

app/testpmd: add commands for filters

add commands in testpmd for NIC filters:
add_ethertype_filter
remove_ethertype_filter
get_ethertype_filter
add_2tuple_filter
remove_2tuple_filter
get_2tuple_filter
add_5tuple_filter
remove_5tuple_filter
get_5tuple_filter
add_syn_filter
remove_syn_filter
get_syn_filter
add_flex_filter
remove_flex_filter
get_flex_filter

Signed-off-by: jingjing.wu <jingjing.wu@intel.com>
Tested-by: Waterman Cao <waterman.cao@intel.com>
Reviewed-by: Vladimir Medvedkin <medvedkinv@gmail.com>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>