tools lib bpf: Rename set_private() to set_priv()

tools lib bpf: Rename set_private() to set_priv()

For consistency with class__priv() elsewhere, and with the callback
typedef for clearing those areas (e.g. bpf_map_clear_priv_t).

Acked-by: Wang Nan <wangnan0@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/n/tip-rnbiyv27ohw8xppsgx0el3xb@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>