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

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: aa52bcbe0e72 ("tools: bpftool: Fix json dump crash on powerpc")
Signed-off-by: Gu Shengxian <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Link: https://lore.kernel.org/bpf/[e-mail]

tools/bpf/bpftool/jit_disasm.c

···
 {
 	va_list ap;
 	char *s;
+	int err;
 
 	va_start(ap, fmt);
-	if (vasprintf(&s, fmt, ap) < 0)
-		return -1;
+	err = vasprintf(&s, fmt, ap);
 	va_end(ap);
+	if (err < 0)
+		return -1;
 
 	if (!oper_count) {
 		int i;