netlink plugin: fix truncation warnings

netlink plugin: fix truncation warnings

  CC       src/netlink_la-netlink.lo
src/netlink.c: In function ‘qos_filter_cb’:
src/netlink.c:544:58: warning: ‘%s’ directive output may be truncated writing up to 127 bytes into a region of size between 121 and 122 [-Wformat-truncation=]
       snprintf(type_instance, sizeof(type_instance), "%s-%s", tc_type, tc_inst);
                                                          ^~            ~~~~~~~
src/netlink.c:544:7: note: ‘snprintf’ output between 7 and 135 bytes into a destination of size 128
       snprintf(type_instance, sizeof(type_instance), "%s-%s", tc_type, tc_inst);
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/netlink.c:577:58: warning: ‘%s’ directive output may be truncated writing up to 127 bytes into a region of size between 121 and 122 [-Wformat-truncation=]
       snprintf(type_instance, sizeof(type_instance), "%s-%s", tc_type, tc_inst);
                                                          ^~            ~~~~~~~
src/netlink.c:577:7: note: ‘snprintf’ output between 7 and 135 bytes into a destination of size 128
       snprintf(type_instance, sizeof(type_instance), "%s-%s", tc_type, tc_inst);
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  CCLD     netlink.la