bpftool: Properly close va_list 'ap' by va_end() on error

bpftool: Properly close va_list 'ap' by va_end() on error

commit bc832065b60f973771ff3e657214bb21b559833c upstream.

va_list 'ap' was opened but not closed by va_end() in error case. It should
be closed by va_end() before the return.

Fixes: 4f34379a7566 ("tools: bpftool: Fix json dump crash on powerpc")
Signed-off-by: Gu Shengxian <gushengxian@yulong.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: https://lore.kernel.org/bpf/20210706013543.671114-1-gushengxian507419@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>