libbpf: fix an snprintf() overflow check

The snprintf() function returns the number of bytes it *would* have
copied if there were enough space.  So it can return > the
sizeof(gen->attach_target).

Fixes: 67234743 ("libbpf: Generate loader program out of BPF ELF file.")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/YtZ+oAySqIhFl6/J@kiliSigned-off-by: Alexei Starovoitov <ast@kernel.org>

tools/lib/bpf/gen_loader.c

@@ -533,7 +533,7 @@ void bpf_gen__record_attach_target(struct bpf_gen *gen, const char *attach_name,
 	gen->attach_kind = kind;
 	ret = snprintf(gen->attach_target, sizeof(gen->attach_target), "%s%s",
 		       prefix, attach_name);
-	if (ret == sizeof(gen->attach_target))
+	if (ret >= sizeof(gen->attach_target))
 		gen->error = -ENOSPC;
 }