tc: flower: fix print with oneline option

tc: flower: fix print with oneline option

This commit fix all location in flower to use _SL_ instead of \n for
newline to allow support for oneline option.

Example before this commit:

filter protocol ip pref 2 flower chain 0 handle 0x1
  indev ens1f0
  dst_mac 11:22:33:44:55:66
  eth_type ipv4
  ip_proto tcp
  src_ip 2.2.2.2
  src_port 99
  dst_port 1-10\  tcp_flags 0x5/5
  ip_flags frag
  ct_state -trk\  ct_zone 4\  ct_mark 255
  ct_label 00000000000000000000000000000000
  skip_hw
  not_in_hw\    action order 1: ct zone 5 pipe
         index 1 ref 1 bind 1 installed 287 sec used 287 sec
        Action statistics:\     Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
        backlog 0b 0p requeues 0\

Example output after this commit:

filter protocol ip pref 2 flower chain 0 handle 0x1 \  indev ens1f0\  dst_mac 11:22:33:44:55:66\  eth_type ipv4\  ip_proto tcp\  src_ip 2.2.2.2\  src_port 99\  dst_port 1-10\  tcp_flags 0x5/5\  ip_flags frag\  ct_state -trk\  ct_zone 4\  ct_mark 255\  ct_label 00000000000000000000000000000000\  skip_hw\  not_in_hw\action order 1: ct zone 5 pipe
         index 1 ref 1 bind 1 installed 346 sec used 346 sec
        Action statistics:\     Sent 0 bytes 0 pkt (dropped 0, overlimits 0 requeues 0)
        backlog 0b 0p requeues 0\

Signed-off-by: Roi Dayan <roid@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>